**Destruction of Medical N2O in Sweden**

#### Mats Ek and Kåre Tjus

*IVL Swedish Environmental Research Institute Sweden* 

#### **1. Introduction**

184 Greenhouse Gases – Capturing, Utilization and Reduction

Wanat, E. C.; Venkataraman K. & Schmidt L. D. (2004) Steam reforming and water–gas shift

Wang, C.-B.; Lee, C.-C.; Bi, J.-L.; Siang, J.-Y.; Liu, J.-Y. & Yeh C.-T. (2009) Study on the steam reforming of ethanol over cobalt oxides, Catalysis Today 146, 76–81 Wei, J. & Iglesia E. (2004) Structural and Mechanistic Requirements for Methane Activation

Whitaker, F. L. & Lueckel, W. J. (1994) The phosphoric acid PC25 fuel cell power plant and beyond, Proceedings of the American Power Conference 56(1), 177-8 Yamazaki, T.; Naoko, K.; Katoh, M.; Hirose, T.; Saito, H.; Yoshikawa T. & Mamoru, W.

Yamazaki, T.; Naoko, K.; Katoh, M.; Hirose, T.; Saito, H.; Yoshikawa, T. & Mamoru, W.

Zhang, B.; Cai, W.; Li Y., Xu, Y. & Shen, W. (2008) Hydrogen production by steam reforming

catalyst, International Journal of Hydrogen and Energy 33, 4377-4386 Zhang, L.; Li, W.; Liu, J.; Guo, C.; Wang, Y. & Zhang J. (2009) Ethanol steam reforming reactions over Al2O3/SiO2-supported Ni–La catalysts, Fuel 88, 511–518

A: General 276, 155–162

Applied Catalysis B: Environmental 99, 81–88

Applied Catalysis B: Environmental 99, 81–88

43, 3685 –3688

of ethanol on Rh and Rh–Ce catalysts in a catalytic wall reactor, Applied Catalysis

and Chemical Conversion on Supported Iridium Clusters, Angew. Chem. Int. Ed.

(2010) Behavior of steam reforming reaction for bio-ethanol over Pt/ZrO2 catalysts,

(2010) Behavior of steam reforming reaction for bio-ethanol over Pt/ZrO2 catalysts,

of ethanol over an Ir/CeO2 catalyst: Reaction mechanism and stability of the

The potent greenhouse gas nitrous oxide (N2O) is widely used in Sweden and many other countries as a mild anaesthetic or pain relief for mothers in labour. The Stockholm County Council (SCC) realized that the nitrous oxide used was responsible for a significant part of the total emission of greenhouse gases from their activities, including public transport. In 2002 SCC started to look for economically and environmentally sound ways to stop or lower the emission. Since nitrous oxide is effective, cheap, easy to use and without risks for mother or baby the maternity wards wanted to continue to use it as one of several methods for pain relief.

Different ways to collect and destroy the used nitrous oxide were therefore investigated in co-operation with IVL Swedish Environmental Research Institute (IVL). Efforts were soon concentrated on an existing Japanese unit treating mixed anaesthetic gases from operation (Kai et al, 2002). This was rebuilt for the new purpose by Showa Denko K.K., and installed in one of Stockholm's main hospitals in 2004. The unit called Anaesclean-SW was effective and reliable from start, and destroyed more than 95 % of the collected gas. Life Cycle Assessment (LCA) and Life Cycle Cost (LCC) showed that the method was both environmentally and economically sound (Ek & Tjus 2008). The results were so good that SCC as one of their environmental goals said that the emission of nitrous oxide from the hospitals in 2011 should have decreased by 75 % as compared to that in 2002.

This chapter will discuss the development in Stockholm and the rest of Sweden up till now. It includes


There are now 12 units running in Sweden. LCA and LCC for the latest ones will be given, and the future development discussed.

#### **2. Different ways to decrease the emission of N2O from hospitals**

The use of N2O in Swedish hospitals has decreased during the last years, but it was still about 155 tons in 2009 (Borgendahl, 2011). Since 1 kg N2O has the same effect as greenhouse

Destruction of Medical N2O in Sweden 187

Since the negative effect on occupational health has been known for a long time, the delivery wards already have systems to reduce the concentration of N2O in the delivery rooms. The distributing masks are also collecting most of the gas in the exhalation, and this is ventilated

In Sweden different types of masks and suction systems are used. In the so called single masks there is just one compartment in the mask, and both inlet of N2O and suction of exhalation gas are connected to this. The suction is normally via an ejector pump in the main ventilation shaft, and the capacity is about 25 L/min. The collected N2O is considerably diluted in the shaft, to concentrations of about 50-100 ppm. As will be discussed later this is

In many hospitals there is a more powerful and separate exhaust system. This uses double masks, with one central compartment where the gas is distributed, and a surrounding compartment where the exhaled air is collected, mixed with some of the surrounding air, and sucked out with a fan. This fan normally has a capacity of about 500 L/min, and it has its own outlet tube to the atmosphere. This system can collect more of the exhaled N2O, and

Fig. 1. A midwife demonstrates the use of a double mask. (Photo Mattias Ahlm)

Studies of systems with double masks have shown that 70-75 % of the used gas is collected by the mask (SLL, 2008). The figure varies a lot between deliveries, dependent on the handling of the mask. As much as 25-30 % of the used N2O is lost to the room atmosphere

**2.2 Collection of used N2O** 

out of the room in different ways.

a serious drawback for destruction.

the concentration is higher in spite of the high air flow.

gas as 298 kg CO2, this corresponds to about 46 000 tons of CO2. It is a small part of the total emission of N2O from Sweden, that was reported to be about 23 000 tons N2O in 2009 (UNFCCC, 2011) but it is easier to influence than the emissions from agriculture which is the totally dominating source. About 90 % of the total amount of N2O used in the Swedish hospitals is estimated to be used for pain relief during labour, and the rest mainly for surgical operation and special dental care. N2O is stable in the patient lung and blood system, and all the used gas is finally emitted from the body.

In 2002 the environmental director of SCC, Åke Wennmalm, pointed out that N2O used in delivery in Stockholm was responsible for a significant part of the total globing warming potential from the SCC. Electricity was mainly from renewable sources, and the transport sector was rapidly going over to non-fossil fuel. A broad and long-term work was started to decrease the emissions of N2O. Several steps in the chain of N2O use were studied.

#### **2.1 Decreased use of N2O**

The most direct way to reduce the emission of N2O is to reduce the use. In surgical operation N2O is now used just in small quantities, combined with other anaesthetics. The use is minimized by circulation of the anaesthetics in the breathing air. This is possible since the patient is anaesthetised and the breathing mask is firmly attached to the patient. Recirculation of N2O is much more difficult in delivery or dental care with more open systems. It is important that the mother in labour pain can dose the pain relieve herself, without the aid of medical professionals. This means that she just uses the mask with gas when she is in pain, most of the time she doesn't use the mask.

If it is difficult to reduce the use of N2O in delivery, why not use other methods? There are several, like epidural, uterine and pelvic anaesthesia. However, most anaesthetics in Sweden consider N2O to be the best method in normal birth, since it can be handled by the mother herself, it is cheap and it is without known negative side effects on children and mothers. N2O is now used in about 70 % of the births in Sweden (Borgendahl, 2011). Other countries with more than 50 % use of N2O are Finland, Norway, England, Australia and New Zealand. In Canada it is used in 20-30 % of all births, while it is very rare now in USA. There is a debate now in USA to again start to offer N2O as an alternative method, mainly due to the low cost and easy handling by the mothers themselves. But there are also two negative aspects when using N2O. Besides the strong effect as a greenhouse gas, it can also affect the health of the delivery ward personnel negatively during long time exposure (Berge, 2001). The occupational health 8 h limit value in Sweden is 100 ppm N2O.

Of course all N2O that is purchased should be used by the patients. However, a survey of the often old distribution systems in many hospitals revealed leakage points responsible for up to 20 % of the purchased amount, or even more in some hospitals. Another point of loss of N2O is the residual in pressurised bottles returned to the supplier. Since gases for medical use have to be filled in clean, empty bottles, the residue has to be let out. This can be 5-10 % of the total amount, depending on the practice of the hospital. There has to be a certain safety margin so that there is always gas available. The residual gas is sometimes used for other purposes by the supplier, but in many cases it is (was) just released to the atmosphere. Many County Councils now demand that their supplier destroy the residual N2O that is not used for other purposes.

#### **2.2 Collection of used N2O**

186 Greenhouse Gases – Capturing, Utilization and Reduction

gas as 298 kg CO2, this corresponds to about 46 000 tons of CO2. It is a small part of the total emission of N2O from Sweden, that was reported to be about 23 000 tons N2O in 2009 (UNFCCC, 2011) but it is easier to influence than the emissions from agriculture which is the totally dominating source. About 90 % of the total amount of N2O used in the Swedish hospitals is estimated to be used for pain relief during labour, and the rest mainly for surgical operation and special dental care. N2O is stable in the patient lung and blood

In 2002 the environmental director of SCC, Åke Wennmalm, pointed out that N2O used in delivery in Stockholm was responsible for a significant part of the total globing warming potential from the SCC. Electricity was mainly from renewable sources, and the transport sector was rapidly going over to non-fossil fuel. A broad and long-term work was started to

The most direct way to reduce the emission of N2O is to reduce the use. In surgical operation N2O is now used just in small quantities, combined with other anaesthetics. The use is minimized by circulation of the anaesthetics in the breathing air. This is possible since the patient is anaesthetised and the breathing mask is firmly attached to the patient. Recirculation of N2O is much more difficult in delivery or dental care with more open systems. It is important that the mother in labour pain can dose the pain relieve herself, without the aid of medical professionals. This means that she just uses the mask with gas

If it is difficult to reduce the use of N2O in delivery, why not use other methods? There are several, like epidural, uterine and pelvic anaesthesia. However, most anaesthetics in Sweden consider N2O to be the best method in normal birth, since it can be handled by the mother herself, it is cheap and it is without known negative side effects on children and mothers. N2O is now used in about 70 % of the births in Sweden (Borgendahl, 2011). Other countries with more than 50 % use of N2O are Finland, Norway, England, Australia and New Zealand. In Canada it is used in 20-30 % of all births, while it is very rare now in USA. There is a debate now in USA to again start to offer N2O as an alternative method, mainly due to the low cost and easy handling by the mothers themselves. But there are also two negative aspects when using N2O. Besides the strong effect as a greenhouse gas, it can also affect the health of the delivery ward personnel negatively during long time exposure (Berge, 2001).

Of course all N2O that is purchased should be used by the patients. However, a survey of the often old distribution systems in many hospitals revealed leakage points responsible for up to 20 % of the purchased amount, or even more in some hospitals. Another point of loss of N2O is the residual in pressurised bottles returned to the supplier. Since gases for medical use have to be filled in clean, empty bottles, the residue has to be let out. This can be 5-10 % of the total amount, depending on the practice of the hospital. There has to be a certain safety margin so that there is always gas available. The residual gas is sometimes used for other purposes by the supplier, but in many cases it is (was) just released to the atmosphere. Many County Councils now demand that their supplier destroy the residual N2O that is not

decrease the emissions of N2O. Several steps in the chain of N2O use were studied.

system, and all the used gas is finally emitted from the body.

when she is in pain, most of the time she doesn't use the mask.

The occupational health 8 h limit value in Sweden is 100 ppm N2O.

**2.1 Decreased use of N2O** 

used for other purposes.

Since the negative effect on occupational health has been known for a long time, the delivery wards already have systems to reduce the concentration of N2O in the delivery rooms. The distributing masks are also collecting most of the gas in the exhalation, and this is ventilated out of the room in different ways.

In Sweden different types of masks and suction systems are used. In the so called single masks there is just one compartment in the mask, and both inlet of N2O and suction of exhalation gas are connected to this. The suction is normally via an ejector pump in the main ventilation shaft, and the capacity is about 25 L/min. The collected N2O is considerably diluted in the shaft, to concentrations of about 50-100 ppm. As will be discussed later this is a serious drawback for destruction.

In many hospitals there is a more powerful and separate exhaust system. This uses double masks, with one central compartment where the gas is distributed, and a surrounding compartment where the exhaled air is collected, mixed with some of the surrounding air, and sucked out with a fan. This fan normally has a capacity of about 500 L/min, and it has its own outlet tube to the atmosphere. This system can collect more of the exhaled N2O, and the concentration is higher in spite of the high air flow.

Fig. 1. A midwife demonstrates the use of a double mask. (Photo Mattias Ahlm)

Studies of systems with double masks have shown that 70-75 % of the used gas is collected by the mask (SLL, 2008). The figure varies a lot between deliveries, dependent on the handling of the mask. As much as 25-30 % of the used N2O is lost to the room atmosphere

Destruction of Medical N2O in Sweden 189

A third method to break the N2O molecule is to split it into nitrogen gas, N2, and oxygen, O2. This can be done with a catalyst at temperatures about 400-500°C, without any addition. As with the other methods the catalyst has to be heated all the time, so energy recovery from the treated gas is important in order to improve the environmental performance and reduce cost. In 2002, when the method had to be decided, this seemed to be the most promising method. At that time there was a presentation of a Japanese system that treated exhaust gas from surgical operation (Kai et al., 2002). It removed other anaesthetic gases and split N2O catalytically. After discussions between SCC and Showa Denko K.K. the Japanese company started to investigate the possibilities to treat N2O in much lower concentration than in Japan, and without other anaesthetic gases. After it was shown that the process created no

Early in 2004 SCC made an international enquiry for tenders. The only final offer was given by Showa Denko. There were obviously no other systems close to commercialisation. The first unit, called Anesclean SW, was installed at Huddinge hospital in southern Stockholm in

or very little NOX the process was a candidate for delivery wards in SCC.

Inlet N2O concentration meter (IR based flow through system), Textile particle filter to minimise clogging of the catalyst bed,

Heat exchanger between inlet and outlet gas to the catalyst bed,

A fan to dilute the treated gas, to cool it further before discharge to atmosphere.

Heat recovery was from start considered to be important, due to the great amount of air that passed the catalyst and cooled it down. The temperature of the treated air stream before mixing with ambient air was about 80°C when the catalyst temperature was 400°C. The catalyst, being the heart of the system, had a secret composition and manufacturing process,

The 11 delivery rooms at Huddinge hospital already had double masks and efficient exhaust system (Anevac) so Anesclean SW could just be connected to the suction system outlet. The Anevac system is common to all 11 rooms, but the valve to each room is closed as long as no N2O is used there. When a mother wants pain relief the first time the personnel activates the system, and the mother can breathe in a mixture of oxygen and N2O whenever she wants. The suction system is automatically activated and about 500 L/min is from now on sucked out through the mask. This continues until the N2O system is turned off, normally after the birth. This means that the 500 L/min for long periods, between the worst labour pains, is mainly air. When the mother uses N2O the concentration can be up to 30 000 ppm in peaks.

**2.3.3 Catalytic splitting** 

**3. Installed destruction units** 

**3.1 Generation 1** 

December 2004.

Air flow meter,

Anesclean SW consisted of

Fan with manual speed control,

The catalyst bed with electric heating, Outlet N2O concentration meter and

but was mainly 5 % rhodium on aluminium oxide.

and evacuated by the main ventilation. One reason is imperfect handling of the mask; this is not the main concern of the mother at the time. Some gas leaks out beside the mask.

Another reason is that the gas dissolved in the mothers blood is ventilated out during several exhalations after she has stopped inhaling the gas. This means that the mask should be used for exhalation for half a minute or more, without inhalation through it, after the pain has decreased. With special instruction about this the collection ratio was shown to increase to 80-85 % (SLL, 2010).

A small step in this direction is the new practice with the mask in a string around the mother's neck. In this way the mask continues to suck out some of the exhalation air even if the mother is walking around in the room.

#### **2.3 Ways to destruct N2O**

When most of the used N2O is collected in a relatively concentrated stream it is possible to destroy it in different ways. It is also possible to separate N2O from the air stream for purification and reuse. However, the relatively low capacity of e.g. zeolites, cost of purification of a medical gas and the low price of new N2O make this less interesting.

N2O is a quite stable gas, but like most chemical compounds, it can be oxidised or reduced, depending on conditions.

#### **2.3.1 Oxidation**

Oxidation here means introduction of more oxygen in the molecule, giving compounds like NO2, or in general NOX with X > 0.5. Just mixing N2O and oxygen (or air) is not enough, but in conventional combustion the temperature is enough. High concentrations of N2O can be incinerated without extra fuel, but for the concentrations in the delivery exhaust external fuel has to be added. This fuel and the incinerator are of course extra costs, and can only be justified if the heat energy is needed close to the hospital. Today most of the Swedish hospitals are connected to district heating systems, and don't have furnaces. However, experiments with combustion in a hospital furnace still in use have been performed. It showed that the NOX production was so high that the experiments were stopped (Engman, 2011).

N2O can also be oxidised at lower concentrations by using a heated catalyst. No extra fuel is needed, but the catalyst has to be heated in some way all the time, since the reaction is not exothermic enough. Also in this process NOX is formed, with its negative environmental impact.

#### **2.3.2 Catalytic reduction**

Reduction here means removal of oxygen, and the result is N2, nitrogen gas that constitutes most of our atmosphere. On the catalyst something else has to be oxidised, like any organic gas or hydrogen gas. The temperature of the catalyst doesn't have to be so high, but the problem is the high concentration of oxygen in the collected exhaust gas. This is about 20 %, compared to about 0.2 % of N2O. This means that a lot of organic material or hydrogen gas has to be added to reduce the oxygen to water before most of the N2O is reduced. To be of interest the catalyst has to very selective for N2O.

#### **2.3.3 Catalytic splitting**

188 Greenhouse Gases – Capturing, Utilization and Reduction

and evacuated by the main ventilation. One reason is imperfect handling of the mask; this is

Another reason is that the gas dissolved in the mothers blood is ventilated out during several exhalations after she has stopped inhaling the gas. This means that the mask should be used for exhalation for half a minute or more, without inhalation through it, after the pain has decreased. With special instruction about this the collection ratio was shown to

A small step in this direction is the new practice with the mask in a string around the mother's neck. In this way the mask continues to suck out some of the exhalation air even if

When most of the used N2O is collected in a relatively concentrated stream it is possible to destroy it in different ways. It is also possible to separate N2O from the air stream for purification and reuse. However, the relatively low capacity of e.g. zeolites, cost of purification of a medical gas and the low price of new N2O make this less interesting.

N2O is a quite stable gas, but like most chemical compounds, it can be oxidised or reduced,

Oxidation here means introduction of more oxygen in the molecule, giving compounds like NO2, or in general NOX with X > 0.5. Just mixing N2O and oxygen (or air) is not enough, but in conventional combustion the temperature is enough. High concentrations of N2O can be incinerated without extra fuel, but for the concentrations in the delivery exhaust external fuel has to be added. This fuel and the incinerator are of course extra costs, and can only be justified if the heat energy is needed close to the hospital. Today most of the Swedish hospitals are connected to district heating systems, and don't have furnaces. However, experiments with combustion in a hospital furnace still in use have been performed. It showed that the NOX production was so high that the experiments were stopped (Engman,

N2O can also be oxidised at lower concentrations by using a heated catalyst. No extra fuel is needed, but the catalyst has to be heated in some way all the time, since the reaction is not exothermic enough. Also in this process NOX is formed, with its negative environmental

Reduction here means removal of oxygen, and the result is N2, nitrogen gas that constitutes most of our atmosphere. On the catalyst something else has to be oxidised, like any organic gas or hydrogen gas. The temperature of the catalyst doesn't have to be so high, but the problem is the high concentration of oxygen in the collected exhaust gas. This is about 20 %, compared to about 0.2 % of N2O. This means that a lot of organic material or hydrogen gas has to be added to reduce the oxygen to water before most of the N2O is reduced. To be of

not the main concern of the mother at the time. Some gas leaks out beside the mask.

increase to 80-85 % (SLL, 2010).

**2.3 Ways to destruct N2O** 

depending on conditions.

**2.3.1 Oxidation** 

2011).

impact.

**2.3.2 Catalytic reduction** 

interest the catalyst has to very selective for N2O.

the mother is walking around in the room.

A third method to break the N2O molecule is to split it into nitrogen gas, N2, and oxygen, O2. This can be done with a catalyst at temperatures about 400-500°C, without any addition. As with the other methods the catalyst has to be heated all the time, so energy recovery from the treated gas is important in order to improve the environmental performance and reduce cost. In 2002, when the method had to be decided, this seemed to be the most promising method. At that time there was a presentation of a Japanese system that treated exhaust gas from surgical operation (Kai et al., 2002). It removed other anaesthetic gases and split N2O catalytically. After discussions between SCC and Showa Denko K.K. the Japanese company started to investigate the possibilities to treat N2O in much lower concentration than in Japan, and without other anaesthetic gases. After it was shown that the process created no or very little NOX the process was a candidate for delivery wards in SCC.

#### **3. Installed destruction units**

#### **3.1 Generation 1**

Early in 2004 SCC made an international enquiry for tenders. The only final offer was given by Showa Denko. There were obviously no other systems close to commercialisation. The first unit, called Anesclean SW, was installed at Huddinge hospital in southern Stockholm in December 2004.

Anesclean SW consisted of Inlet N2O concentration meter (IR based flow through system), Textile particle filter to minimise clogging of the catalyst bed, Fan with manual speed control, Air flow meter, Heat exchanger between inlet and outlet gas to the catalyst bed, The catalyst bed with electric heating, Outlet N2O concentration meter and A fan to dilute the treated gas, to cool it further before discharge to atmosphere.

Heat recovery was from start considered to be important, due to the great amount of air that passed the catalyst and cooled it down. The temperature of the treated air stream before mixing with ambient air was about 80°C when the catalyst temperature was 400°C. The catalyst, being the heart of the system, had a secret composition and manufacturing process, but was mainly 5 % rhodium on aluminium oxide.

The 11 delivery rooms at Huddinge hospital already had double masks and efficient exhaust system (Anevac) so Anesclean SW could just be connected to the suction system outlet. The Anevac system is common to all 11 rooms, but the valve to each room is closed as long as no N2O is used there. When a mother wants pain relief the first time the personnel activates the system, and the mother can breathe in a mixture of oxygen and N2O whenever she wants. The suction system is automatically activated and about 500 L/min is from now on sucked out through the mask. This continues until the N2O system is turned off, normally after the birth. This means that the 500 L/min for long periods, between the worst labour pains, is mainly air. When the mother uses N2O the concentration can be up to 30 000 ppm in peaks.

Destruction of Medical N2O in Sweden 191

Of the N2O entering the Anesclean SW over 97 % was destroyed during the first year of operation. The availability of the system was high, over 99 %, without any maintenance. The short stop periods were due to testing of the back-up energy system at the hospital each

The only problem with this first generation was the high consumption of energy. Due to the constantly high air flow rate it used about 35 kWh/kg N2O destroyed. This is coupled to the

After the successful installation of this first unit SCC decided to go on with installations in other hospitals. After some discussion about licence fees the Swedish company QMT in 2008 installed the second unit in Danderyd hospital in the northern part of Stockholm. The design was similar to the original one delivered by Showa Denko at Huddinge hospital, with the

There were some important differences however. The one big unit was divided in two, with a separate part for gas analyses and regulation of the unit. This was mainly to make it easier to install in crowded areas. Extra heat exchangers were added to recover as much as possible of the energy used. But the most important change was on line regulation of the amount of air that was actually treated. This was done by measuring the airflow from the exhaust system Anevac, and setting the fan capacity slightly higher. In this way all the collected air was treated and very little air from outside was added. This resulted in average N2O concentration about 2 400 ppm, compared to about 900 ppm in the first generation unit

Experience showed no problems to keep the temperature in the catalyst bed constant, and the overall destruction of collected N2O was more than 98 %. Mainly due to the regulation of air flow the specific energy demand was decreased to about 10 kWh/kg N2O destroyed.

One remaining drawback with the unit was the big size, which made it difficult to install in some hospitals. The price was also relatively high, especially for smaller hospitals with fewer deliveries. By now a new Swedish company Nordic Gas Cleaning, NGC, had developed their own system, with another catalyst without rhodium or other rare metals, built in modules and with simpler casing. The typical NGC unit is smaller and considerably lighter, about 1.0 x 3.3 m footprint, 2 m high and 1 400 kg (figure 4), compared to the first Anesclean SW with footprint 1.6 x 3.0 m, 2 m high and about 3 500 kg for the same number

The later NGC units also have another system for heat recovery. Instead of the conventional gas/gas heat exchangers it uses ceramic heat storage systems, one on each side of the catalyst. Heating is still just in the catalyst itself, to about 500°C in their case. Hot air leaving the catalyst heats up ceramic bed 2. When the temperature in ceramic bed 1 has dropped to about 60°C, the flow direction changes and ceramic bed 1 is heated by the treated air while bed 2 is preheating air going in to the catalyst bed. Flow direction is changed about every 2- 3 minutes. When changing flow direction a small amount of air doesn't pass the catalyst, but

relatively low average concentration of about 900 ppm N2O in the treated air.

month. Then the unit had to be restarted manually.

with the same number of delivery rooms connected.

**3.2 Generation 2** 

same catalyst.

**3.3 Generation 3** 

of delivery rooms.

500 L/min is not an exact figure; it is regulated by certain under pressure in the system. When there is no room activated there is still a base air flow, due to small intentional leaks in the system. This is illustrated in figure 2. There were hours with no N2O to destroy, but still there was an air flow of 1 m3/min in this period. For short periods there were up to 5 or 6 rooms connected. This is a problem since the fan in Anesclean had to be changed manually. In practice you had to decide which air flow to set in order to collect most of the exhaust gas most of the time. In this case it was set to 2.3 m3/min, based upon flow rates and concentrations measured over a long period.

Fig. 2. Variation of gas flow rate in the Anevac system dependent on the number of mothers using N2O.

Not just the flow rate varies quickly over time. The concentration of N2O varies even more, for this installation between 0 and about 10 000 ppm. This is illustrated in figure 3. The reason to have constant flow rate in Anesclean SW was fear about the temperature control of the catalyst not being able to follow fast variations in flow rate, and thus cooling. With this fixed air flow rate of 2.3 m3/min in average about 5 % of the collected N2O from the Anevac system wasn't taken into the Anesclean SW, it was directly led to the atmosphere.

Fig. 3. Variation of concentration of N2O in the Anevac system, average concentration about 700 ppm.

Of the N2O entering the Anesclean SW over 97 % was destroyed during the first year of operation. The availability of the system was high, over 99 %, without any maintenance. The short stop periods were due to testing of the back-up energy system at the hospital each month. Then the unit had to be restarted manually.

The only problem with this first generation was the high consumption of energy. Due to the constantly high air flow rate it used about 35 kWh/kg N2O destroyed. This is coupled to the relatively low average concentration of about 900 ppm N2O in the treated air.

#### **3.2 Generation 2**

190 Greenhouse Gases – Capturing, Utilization and Reduction

500 L/min is not an exact figure; it is regulated by certain under pressure in the system. When there is no room activated there is still a base air flow, due to small intentional leaks in the system. This is illustrated in figure 2. There were hours with no N2O to destroy, but still there was an air flow of 1 m3/min in this period. For short periods there were up to 5 or 6 rooms connected. This is a problem since the fan in Anesclean had to be changed manually. In practice you had to decide which air flow to set in order to collect most of the exhaust gas most of the time. In this case it was set to 2.3 m3/min, based upon flow rates

2005-04-19 2005-04-21 2005-04-23 2005-04-25 2005-04-27

Fig. 2. Variation of gas flow rate in the Anevac system dependent on the number of mothers

Not just the flow rate varies quickly over time. The concentration of N2O varies even more, for this installation between 0 and about 10 000 ppm. This is illustrated in figure 3. The reason to have constant flow rate in Anesclean SW was fear about the temperature control of the catalyst not being able to follow fast variations in flow rate, and thus cooling. With this fixed air flow rate of 2.3 m3/min in average about 5 % of the collected N2O from the Anevac

Fig. 3. Variation of concentration of N2O in the Anevac system, average concentration about

system wasn't taken into the Anesclean SW, it was directly led to the atmosphere.

and concentrations measured over a long period.

0,0 0,5 1,0 1,5 2,0 2,5 3,0 3,5

**m3/min**

using N2O.

700 ppm.

After the successful installation of this first unit SCC decided to go on with installations in other hospitals. After some discussion about licence fees the Swedish company QMT in 2008 installed the second unit in Danderyd hospital in the northern part of Stockholm. The design was similar to the original one delivered by Showa Denko at Huddinge hospital, with the same catalyst.

There were some important differences however. The one big unit was divided in two, with a separate part for gas analyses and regulation of the unit. This was mainly to make it easier to install in crowded areas. Extra heat exchangers were added to recover as much as possible of the energy used. But the most important change was on line regulation of the amount of air that was actually treated. This was done by measuring the airflow from the exhaust system Anevac, and setting the fan capacity slightly higher. In this way all the collected air was treated and very little air from outside was added. This resulted in average N2O concentration about 2 400 ppm, compared to about 900 ppm in the first generation unit with the same number of delivery rooms connected.

Experience showed no problems to keep the temperature in the catalyst bed constant, and the overall destruction of collected N2O was more than 98 %. Mainly due to the regulation of air flow the specific energy demand was decreased to about 10 kWh/kg N2O destroyed.

#### **3.3 Generation 3**

One remaining drawback with the unit was the big size, which made it difficult to install in some hospitals. The price was also relatively high, especially for smaller hospitals with fewer deliveries. By now a new Swedish company Nordic Gas Cleaning, NGC, had developed their own system, with another catalyst without rhodium or other rare metals, built in modules and with simpler casing. The typical NGC unit is smaller and considerably lighter, about 1.0 x 3.3 m footprint, 2 m high and 1 400 kg (figure 4), compared to the first Anesclean SW with footprint 1.6 x 3.0 m, 2 m high and about 3 500 kg for the same number of delivery rooms.

The later NGC units also have another system for heat recovery. Instead of the conventional gas/gas heat exchangers it uses ceramic heat storage systems, one on each side of the catalyst. Heating is still just in the catalyst itself, to about 500°C in their case. Hot air leaving the catalyst heats up ceramic bed 2. When the temperature in ceramic bed 1 has dropped to about 60°C, the flow direction changes and ceramic bed 1 is heated by the treated air while bed 2 is preheating air going in to the catalyst bed. Flow direction is changed about every 2- 3 minutes. When changing flow direction a small amount of air doesn't pass the catalyst, but

Destruction of Medical N2O in Sweden 193

destroy this. High air flow collects more N2O, gives better working environment, but takes a lot of energy for destruction. In all three systems in table 1 the collection system had the same design with double masks and roughly the same air flow per mask (400-500 m3/min).

> Average air flow, m3/min

Generation 1 (2004) 11 2.3 900 35 Generation 2 (2008) 12 1.9 2 400 10 Generation 3 (2010) 12 1.5 1 500 5

Table 1. Energy demand in N2O destruction systems at three hospitals of similar size.

new systems. The destruction ratios for N2O have been 98-99 % in all three systems.

The development over time is obvious, and this has also been the main reason for designing

These are relatively big hospitals and delivery wards. With the same system the specific energy demand increases rapidly for smaller units, with longer periods without N2O used and lower concentrations. To change this a new generation with smart regulation of air flow to the unit has to be developed. Much could be saved by not treating the air completely without N2O. This is both in periods without any birth with N2O (the system not activated) and in periods where the exhaust system is activated but no mother at the moment is breathing N2O. However, as will be seen later, the energy demand in the new units has very

LCA, or Life Cycle Assessment, has been used to evaluate the total environmental impact of the destruction units. Methods and results for the first installation have been reported (SLL, 2005a). All steps are included, from production of equipment material and electricity needed, period of use and finally discharge of the equipment. In all stages use of resources and emissions of different kinds are calculated and sorted into different impact categories.

The functional unit in these calculations was 1 kg of N2O collected by the exhaust gas system. In the case of no destruction the only impact is the potential global warming effect,

With a destruction unit the direct emission of N2O is decreased by about 98 %, leaving 0.02 kg N2O or 5.96 kg CO2-equiv. But production of material needed, transports and electricity also contributes to global warming. This is added to get the total impact of this kind. The

This is a hard work, but still quite scientifically based. The problem comes when you want to compare the possible impacts from one process with another, or in this case no

Average concentration, ppm N2O

Specific energy demand, kWh/kg N2O

Type of unit Delivery

little influence on the total cost.

The most important impact categories here are

Nutrient enrichment/eutrophication and

and this is for 1 kg N2O 298 kg CO2-equivalents.

same is done for all relevant impact categories.

Photochemical ozone formation

Stratospheric ozone depletion

**5. LCA** 

 Global warming Acidification

rooms

this is led through a bed of activated carbon. This N2O is then immediately desorbed and passed through the catalyst before the next change of direction.

Fig. 4. The unit from NGC installed at Södertälje hospital. (Photo Anette Andersson)

In these units the fan and the air flow is regulated by a certain under pressure at the inlet, this means that just a little more air is treated than the amount given by the collection system from the masks. About 98 % of the collected gas is destroyed.

In spite of the higher temperature in the catalyst the specific energy demand is still lower than in the second generation Anesclean SW. With the same loading (i.e. the same number of delivery rooms connected) it is about 5 kWh/kg N2O destroyed. The smaller and more flexible units with both lower energy demand and lower price has resulted in just this third generation type being sold the last two years.

#### **4. Energy savings**

The most important factor for energy demand is the amount of air treated. However, a very good recovery of heat from the treated air also influences the energy used. The specific energy demand, kWh/kg destroyed N2O, is highly dependent on the mean concentration of N2O in the treated air.

The air flow per connected breathing mask is a compromise between working environment and energy saving. Low air flow means less N2O captured, but less energy needed to

this is led through a bed of activated carbon. This N2O is then immediately desorbed and

Fig. 4. The unit from NGC installed at Södertälje hospital. (Photo Anette Andersson)

system from the masks. About 98 % of the collected gas is destroyed.

generation type being sold the last two years.

**4. Energy savings** 

N2O in the treated air.

In these units the fan and the air flow is regulated by a certain under pressure at the inlet, this means that just a little more air is treated than the amount given by the collection

In spite of the higher temperature in the catalyst the specific energy demand is still lower than in the second generation Anesclean SW. With the same loading (i.e. the same number of delivery rooms connected) it is about 5 kWh/kg N2O destroyed. The smaller and more flexible units with both lower energy demand and lower price has resulted in just this third

The most important factor for energy demand is the amount of air treated. However, a very good recovery of heat from the treated air also influences the energy used. The specific energy demand, kWh/kg destroyed N2O, is highly dependent on the mean concentration of

The air flow per connected breathing mask is a compromise between working environment and energy saving. Low air flow means less N2O captured, but less energy needed to

passed through the catalyst before the next change of direction.


destroy this. High air flow collects more N2O, gives better working environment, but takes a


Table 1. Energy demand in N2O destruction systems at three hospitals of similar size.

The development over time is obvious, and this has also been the main reason for designing new systems. The destruction ratios for N2O have been 98-99 % in all three systems.

These are relatively big hospitals and delivery wards. With the same system the specific energy demand increases rapidly for smaller units, with longer periods without N2O used and lower concentrations. To change this a new generation with smart regulation of air flow to the unit has to be developed. Much could be saved by not treating the air completely without N2O. This is both in periods without any birth with N2O (the system not activated) and in periods where the exhaust system is activated but no mother at the moment is breathing N2O. However, as will be seen later, the energy demand in the new units has very little influence on the total cost.

#### **5. LCA**

LCA, or Life Cycle Assessment, has been used to evaluate the total environmental impact of the destruction units. Methods and results for the first installation have been reported (SLL, 2005a). All steps are included, from production of equipment material and electricity needed, period of use and finally discharge of the equipment. In all stages use of resources and emissions of different kinds are calculated and sorted into different impact categories. The most important impact categories here are


The functional unit in these calculations was 1 kg of N2O collected by the exhaust gas system. In the case of no destruction the only impact is the potential global warming effect, and this is for 1 kg N2O 298 kg CO2-equivalents.

With a destruction unit the direct emission of N2O is decreased by about 98 %, leaving 0.02 kg N2O or 5.96 kg CO2-equiv. But production of material needed, transports and electricity also contributes to global warming. This is added to get the total impact of this kind. The same is done for all relevant impact categories.

This is a hard work, but still quite scientifically based. The problem comes when you want to compare the possible impacts from one process with another, or in this case no

Destruction of Medical N2O in Sweden 195

Since the aim of the treatment is to reduce global warming, this category is obviously important, and it is possible to say that this method can decrease the global warming potential from the use of N2O without any strong negative impacts on some of the other common environmental impacts. The same was shown also for the first generation unit from Showa Denko (SLL, 2005a). A complete assessment should, however, also consider the possible discharge of toxic compounds from the manufacture and use of the destruction

The figures used in the LCA are as far as possible based upon actual material production and transports in this case. For electricity Nordic average electricity is used, that is mainly hydropower and nuclear power. This specific hospital uses "green electricity", mainly hydropower, with even less environmental impact. If electricity was based more upon coal, the impact would be higher, but destruction of N2O still appears to perform better than no

Even if the treatment of N2O is environmentally sound, it also has to be economically realistic. If it is too expensive per kg avoided CO2-equivalent, the money should be used for other methods to decrease global warming. To evaluate this LCC, Life Cycle Cost, with the annuity method has been used. This was done for the first Anesclean unit before further

LCC has also been calculated for generation 3 units. Investment cost is here the price of the unit and all costs for installation. Maintenance costs are electricity, service contract and a few hours for local check. The service contract includes changes of catalyst (every 4th year) and fans, and calibration of meters. The residual value is based upon scrap prices and costs

Table 3 shows the result for a big hospital (12 delivery rooms) and equipment from NGC, generation 3. The electricity price for SCC is now about 0.115 €/kWh, and also the double price was used in calculations. The technical and economic lifetime was set to 10 or 15 years, and the interest to 4 or 6 %. Electricity costs, service contract and other personnel costs were

 4 % 0.115 **0.073** 84 % 2.6 % 4 % 0.23 **0.074** 81 % 5.1 % 6 % 0.115 **0.079** 85 % 2.4 % 6 % 0.23 **0.081** 83 % 4.7 % 4 % 0.115 **0.057** 78 % 3.6 % 4 % 0.23 **0.059** 75 % 6.9 % 6 % 0.115 **0.063** 80 % 3.2 % 6 % 0.23 **0.065** 78 % 6.2 %

Table 3. Life Cycle Cost for destruction of N2O with generation 3 equipment in a big

hospital, with different life time, interest rate and electricity cost.

**Specific cost €/kg CO2-eq.**

Capital cost

Electricity cost

Electricity price €/kWh (2011)

equipment, as well as the necessary use of resources.

investments were decided (SLL, 2005b).

for disposal of some components.

supposed to increase by 3 % each year.

Interest rate

destruction.

Life time years

**6. LCC** 

destruction compared to destruction with a well-defined process. The impacts have different units, and some of them are local or regional, while others are global. Which one is most important? Now it is not strictly scientific any more, you can choose different suggested methods to compare the total impact. In this case we show the method with the average annual impact of one person in the world for global impacts and in the EU for regional impacts, table 2. The absolute impacts from the delivery room and the destruction unit are divided by these reference quantities. This is called normalisation. The unit of the normalised values is (European) annual person equivalent. (Hauschild & Wenzel, 2001)


1 kg of the respective impact / year/ person (in the world or in the EU). References per year from the Centre of Environmental Science – Leiden University (CML), version CML2001 – Dec. 07, divided by data from population statistics.

Table 2. Summarized LCA for destruction of N2O in a big hospital with a generation 3 unit, compared to direct emission of 1 kg N2O.

The different units make it impossible to compare the impact of treatment in a strict scientific way. By transforming all impacts to units of annual person equivalents one can at least see the different impacts compared to the impact of an average person in the world or in the EU, as appropriate. The impacts on global warming and eutrophication have the highest figures. For global warming potential it is obvious that treatment of N2O is to prefer, while it is slightly negative for acidification, for photochemical ozone formation near the ground and for the stratospheric ozone destruction potential. If the effect of the destruction unit on eutrophication is positive or negative depends on the fate of the nitrogen of the N2O which is emitted to the environment. If this nitrogen actually contributes to eutrophication, then the destruction unit obviously has a positive impact on eutrophication.

Since the aim of the treatment is to reduce global warming, this category is obviously important, and it is possible to say that this method can decrease the global warming potential from the use of N2O without any strong negative impacts on some of the other common environmental impacts. The same was shown also for the first generation unit from Showa Denko (SLL, 2005a). A complete assessment should, however, also consider the possible discharge of toxic compounds from the manufacture and use of the destruction equipment, as well as the necessary use of resources.

The figures used in the LCA are as far as possible based upon actual material production and transports in this case. For electricity Nordic average electricity is used, that is mainly hydropower and nuclear power. This specific hospital uses "green electricity", mainly hydropower, with even less environmental impact. If electricity was based more upon coal, the impact would be higher, but destruction of N2O still appears to perform better than no destruction.

#### **6. LCC**

194 Greenhouse Gases – Capturing, Utilization and Reduction

destruction compared to destruction with a well-defined process. The impacts have different units, and some of them are local or regional, while others are global. Which one is most important? Now it is not strictly scientific any more, you can choose different suggested methods to compare the total impact. In this case we show the method with the average annual impact of one person in the world for global impacts and in the EU for regional impacts, table 2. The absolute impacts from the delivery room and the destruction unit are divided by these reference quantities. This is called normalisation. The unit of the normalised values is (European) annual person equivalent. (Hauschild & Wenzel, 2001)

> Photochemical ozone formation (regional impact)

equiv. kg C2H4 equiv. kg PO43-

47 0 0 7.3 0

1.0 0.034 0.024 0.16 0.001

1 kg of the respective impact / year/ person (in the world or in the EU). References per year from the Centre of Environmental Science – Leiden University (CML), version CML2001 – Dec. 07, divided by

Table 2. Summarized LCA for destruction of N2O in a big hospital with a generation 3 unit,

The different units make it impossible to compare the impact of treatment in a strict scientific way. By transforming all impacts to units of annual person equivalents one can at least see the different impacts compared to the impact of an average person in the world or in the EU, as appropriate. The impacts on global warming and eutrophication have the highest figures. For global warming potential it is obvious that treatment of N2O is to prefer, while it is slightly negative for acidification, for photochemical ozone formation near the ground and for the stratospheric ozone destruction potential. If the effect of the destruction unit on eutrophication is positive or negative depends on the fate of the nitrogen of the N2O which is emitted to the environment. If this nitrogen actually contributes to eutrophication,

then the destruction unit obviously has a positive impact on eutrophication.

Eutrophication (regional impact)

equiv.

Stratospheric ozone depletion (global impact)

kg CFC11 equiv.

Global warming (global impact)

equiv.

Unit kg CO2

Normalisation

No treatment, annual milliperson equiv.

Destruction, annual milliperson equiv.

data from population statistics.

compared to direct emission of 1 kg N2O.

Acidification (regional impact)

No treatment 298 0 0 0.27 0

Destruction 6.45 0.00117 0.000128 0.00581 2.9 · 10-8

references1 6 310 34 5.3 37 0.029

kg SO2

Even if the treatment of N2O is environmentally sound, it also has to be economically realistic. If it is too expensive per kg avoided CO2-equivalent, the money should be used for other methods to decrease global warming. To evaluate this LCC, Life Cycle Cost, with the annuity method has been used. This was done for the first Anesclean unit before further investments were decided (SLL, 2005b).

LCC has also been calculated for generation 3 units. Investment cost is here the price of the unit and all costs for installation. Maintenance costs are electricity, service contract and a few hours for local check. The service contract includes changes of catalyst (every 4th year) and fans, and calibration of meters. The residual value is based upon scrap prices and costs for disposal of some components.

Table 3 shows the result for a big hospital (12 delivery rooms) and equipment from NGC, generation 3. The electricity price for SCC is now about 0.115 €/kWh, and also the double price was used in calculations. The technical and economic lifetime was set to 10 or 15 years, and the interest to 4 or 6 %. Electricity costs, service contract and other personnel costs were supposed to increase by 3 % each year.


Table 3. Life Cycle Cost for destruction of N2O with generation 3 equipment in a big hospital, with different life time, interest rate and electricity cost.

Destruction of Medical N2O in Sweden 197

environment and the cost per avoided CO2-equivalent is competitive with other ways to

The results from the latest generation of units from NGC show that for small hospitals, with 4 or less delivery rooms, much cheaper units with even less need of service and maintenance

The interest in collection of N2O for destruction has also led to increased efforts to minimize the negative effect on occupational health. The exhaust gas collection has improved, and several measurements of residual concentrations in delivery rooms have

Berge, T. I. (2001) Nitrous oxide in dental surgery. *Best Practice & Research Clinical* 

Borgendahl J. (2011). www.webbhotell.sll.se/lustgaskonsortiet/ Sammanställning över

Hauschild, M. Z. & Wenzel, H. (2001). The European Personal Equivalent: Measuring the

Kai, T.; Kanmura Y.; Takahashi S.; Atobe H. &Hotta M. (2002). Development and utilization

http://www.webbhotell.sll.se/sv/lustgaskonsortiet/Rapporter-och-

http://www.webbhotell.sll.se/sv/lustgaskonsortiet/Rapporter-och-

http://www.webbhotell.sll.se/sv/lustgaskonsortiet/Rapporter-och-

http://www.webbhotell.sll.se/sv/lustgaskonsortiet/Rapporter-och-

study in Sweden. Mitig Adapt Strateg Glob Change 13:809-818.

Engman J. (2011) ÅF Division Infrastructure, personal communication.

Products and Processes (Phase 1). Report no. 242 US EPA.

lustgasförbrukningen inom Sveriges regioner och landsting. (Compilation of laughing gas consumption in Swedish regions and county councils) In Swedish. Ek, M. &Tjus, K. (2008). Decreased emission of nitrous oxide from delivery wards – case

personal environmental space. Annual report NATO/CCMS Pilot Study, Clean

of a system for treating waste anaesthetic gases, ASA abstract. Anaesthesiology

artiklar/Rapporter-från-olika-lustgasprojekt , Lustgasdestruktion, SLL – LCA of a

artiklar/Rapporter-från-olika-lustgasprojekt , Lustgasdestruktion, SLL – LCC for

artiklar/Rapporter-från-olika-lustgasprojekt /Förbättrad insamling, SLL – Insamlingsgrad av lustgas vid förlossning 2008.pdf (Degree of collection of N2O

artiklar/Rapporter-från-olika-lustgasprojekt/ Förbättrad insamling, SLL – Insamlingsgrad med och utan Västeråsmetoden 2010 (Degree of collection with and

have to be developed to give acceptable costs for N2O degradation.

decrease emission of greenhouse gases.

*Anaesthesiology,* 15 (3), 477 – 489.

method to decompose laughing gas.

laughing gas destruction.

from deliveries) In Swedish.

without the Västerås method) In Swedish.

been done.

**10. References** 

96:A574.

SLL (2005a)

SLL (2005b)

SLL (2008).

SLL (2010).

A total cost below 0.1 or even 0.2 €/kg CO2-equivalent is considered as a good investment in SCC for reduction of climate change potential. It is obvious that the totally dominating cost is the capital cost while other factors have little influence. Personnel costs (mainly service contract) and spare parts are 10-15 % of the total cost. For the first unit from Showa Denko the total cost was about 0.099 €/kg CO2-equivalent, and higher proportions on capital cost and electricity (SLL, 2005b). Cheaper units and better energy efficiency has paid off.

For smaller hospitals the cost will rise rapidly. So far the smaller units from NGC are almost as expensive as their bigger ones, they have higher specific energy demands, and destroy much less N2O/year. The unit installed at Södertälje hospital with 6 delivery rooms have a life cycle cost of 0.20 €/kg CO2-equivalent destroyed (15 years, 4 % interest and the lower electricity price). 72 % of this is capital costs, and the service cost has now reached 24 % of the total cost. With the design and technique used today installation in hospitals with less than 5 delivery rooms will have a high cost for each kg CO2-equivalent.

#### **7. Overall emission of N2O in 2010 in SCC**

The total emission of N2O from medical use in SCC has decreased from 33 386 kg in 2002 to 15 959 kg in 2010 (SLL, 2011). This is about 52 % decrease, or about 5 200 tons of CO2 equivalents less than in 2002. This is still far from the environmental goal 75 % decrease to 2011 in SCC. However, with the three new units installed late in 2010 it is quite possible to reach the goal. With the expected destruction in these the calculated decrease from 2002 will be about 72 %. If the emission is related to the number of births in SCC the decrease will be over 75 % since more children are born 2010 and 2011 than in 2002.

Most of the decrease is due to the 5 installed destruction units, but also better control of usage and leaks have contributed. As long as the collected N2O is not more than about 75 % of the used amount it is difficult to reach much further. Now just a few small users like special dentist care are without treatment, and for these new techniques are necessary.

#### **8. Spreading of experience**

After the successful installation and evaluation of the first unit in Stockholm the SCC decided to spread its knowledge and experience to other County Councils. Now all County Councils in Sweden are represented in a N2O consortium that meets via electronic conferences 4-6 times every year and physically at least once a year.

Now in 2011 there are 12 units installed, spread over 4 counties. Discussions are held in others, and there is also interest from other countries.

#### **9. Conclusion**

The focus upon emitted N2O as a significant part of the total greenhouse gas emission from SCC has led to development and installation of several units to destroy N2O used in child delivery. The units have become less expensive, and especially less energy demanding. In big hospitals with many births the installation of destruction units is positive to the environment and the cost per avoided CO2-equivalent is competitive with other ways to decrease emission of greenhouse gases.

The results from the latest generation of units from NGC show that for small hospitals, with 4 or less delivery rooms, much cheaper units with even less need of service and maintenance have to be developed to give acceptable costs for N2O degradation.

The interest in collection of N2O for destruction has also led to increased efforts to minimize the negative effect on occupational health. The exhaust gas collection has improved, and several measurements of residual concentrations in delivery rooms have been done.

#### **10. References**

196 Greenhouse Gases – Capturing, Utilization and Reduction

A total cost below 0.1 or even 0.2 €/kg CO2-equivalent is considered as a good investment in SCC for reduction of climate change potential. It is obvious that the totally dominating cost is the capital cost while other factors have little influence. Personnel costs (mainly service contract) and spare parts are 10-15 % of the total cost. For the first unit from Showa Denko the total cost was about 0.099 €/kg CO2-equivalent, and higher proportions on capital cost and electricity (SLL, 2005b). Cheaper units and better energy efficiency has

For smaller hospitals the cost will rise rapidly. So far the smaller units from NGC are almost as expensive as their bigger ones, they have higher specific energy demands, and destroy much less N2O/year. The unit installed at Södertälje hospital with 6 delivery rooms have a life cycle cost of 0.20 €/kg CO2-equivalent destroyed (15 years, 4 % interest and the lower electricity price). 72 % of this is capital costs, and the service cost has now reached 24 % of the total cost. With the design and technique used today installation in hospitals with less

The total emission of N2O from medical use in SCC has decreased from 33 386 kg in 2002 to 15 959 kg in 2010 (SLL, 2011). This is about 52 % decrease, or about 5 200 tons of CO2 equivalents less than in 2002. This is still far from the environmental goal 75 % decrease to 2011 in SCC. However, with the three new units installed late in 2010 it is quite possible to reach the goal. With the expected destruction in these the calculated decrease from 2002 will be about 72 %. If the emission is related to the number of births in SCC the decrease

Most of the decrease is due to the 5 installed destruction units, but also better control of usage and leaks have contributed. As long as the collected N2O is not more than about 75 % of the used amount it is difficult to reach much further. Now just a few small users like special dentist care are without treatment, and for these new techniques are necessary.

After the successful installation and evaluation of the first unit in Stockholm the SCC decided to spread its knowledge and experience to other County Councils. Now all County Councils in Sweden are represented in a N2O consortium that meets via electronic

Now in 2011 there are 12 units installed, spread over 4 counties. Discussions are held in

The focus upon emitted N2O as a significant part of the total greenhouse gas emission from SCC has led to development and installation of several units to destroy N2O used in child delivery. The units have become less expensive, and especially less energy demanding. In big hospitals with many births the installation of destruction units is positive to the

than 5 delivery rooms will have a high cost for each kg CO2-equivalent.

will be over 75 % since more children are born 2010 and 2011 than in 2002.

conferences 4-6 times every year and physically at least once a year.

others, and there is also interest from other countries.

**7. Overall emission of N2O in 2010 in SCC** 

**8. Spreading of experience** 

**9. Conclusion** 

paid off.


http://www.webbhotell.sll.se/sv/lustgaskonsortiet/Rapporter-och-

artiklar/Rapporter-från-olika-lustgasprojekt , Lustgasdestruktion, SLL – LCA of a method to decompose laughing gas.

#### SLL (2005b)

http://www.webbhotell.sll.se/sv/lustgaskonsortiet/Rapporter-och-

artiklar/Rapporter-från-olika-lustgasprojekt , Lustgasdestruktion, SLL – LCC for laughing gas destruction.

SLL (2008).

http://www.webbhotell.sll.se/sv/lustgaskonsortiet/Rapporter-och-

artiklar/Rapporter-från-olika-lustgasprojekt /Förbättrad insamling, SLL – Insamlingsgrad av lustgas vid förlossning 2008.pdf (Degree of collection of N2O from deliveries) In Swedish.

SLL (2010).

http://www.webbhotell.sll.se/sv/lustgaskonsortiet/Rapporter-och-

artiklar/Rapporter-från-olika-lustgasprojekt/ Förbättrad insamling, SLL – Insamlingsgrad med och utan Västeråsmetoden 2010 (Degree of collection with and without the Västerås method) In Swedish.

**9** 

**Dietary Possibilities to Mitigate** 

Małgorzata Szumacher-Strabel and Adam Cieślak

*Department of Animal Nutrition and Feed Management,* 

*Poznań University of Life Sciences,* 

*RUMEN PULS* 

*Poznań Poland* 

**Rumen Methane and Ammonia Production** 

Efficiency of ruminal metabolism is a significant factor affecting production and release of pollutants, i.e. methane and ammonia. Efficient and balanced ruminal fermentation reduces the emission of gases, particularly methane, to the atmosphere. Losses of energy from the feed ration, connected with the production of methane, are particularly significant in ruminants, since approx. 2/3 production costs are generated by feeds (including forages), fed to animals. Actions aiming at a limitation of methanogenesis in ruminants, at the simultaneous monitoring of quantitative and qualitative changes in methanogens, are justified from the scientific and economic point of view. Proposals of legislative changes include the intention expressed by the European Commission to introduce the so-called *cow* 

Constant temperature on Earth is maintained thanks to a certain type of the greenhouse effect. Solar radiation with a wavelength of 0.1 - 4 μm, reaching the Earth's surface, results in its natural heating, causing the emission of thermal radiation with a wavelength of 4 to 80 μm. Greenhouse gases (GHG) are found in the atmosphere and absorb radiation with an identical wavelength, at the same time causing an elevation of temperature in the lower layers of the atmosphere (IPCC, 2007). Thanks to the above, the mean temperature of the troposphere is by 33°C higher than in case of the absence of an atmosphere, facilitating the development and preservation of life forms on Earth (IPCC, 2007). However, it is estimated that excessive emission of greenhouse gases, caused by human activity, in the last century resulted in the global temperature increasing by 0.5°C. In view of the above the Intergovernmental Panel on Climate Change (IPCC) forecasts that by the year 2100 the temperature on Earth will increase by 1.8 - 3.9°C. This may lead to the melting of ice caps in the Arctic and Antarctic, elevation of sea and ocean levels, continentality of climates, elongation or shortening of the vegetation seasons depending on the latitude, disturbances in air circulation in the atmosphere. Moreover, the above mentioned changes may contribute e.g. to the intensification of tropical cyclones and such phenomena as El Niño or

**1. Introduction** 

*tax*, a tax on kept ruminants.

the Quasi-Biennial Oscillation (QBO; Topping, 2007).

SLL (2011). Miljöredovisning 2010 (Environmental account). In Swedish. UNFCCC (2011).

> http://unfccc.int/national\_reports/annex\_i\_ghg\_inventories/national\_ inventories\_submissions/items/5888.php
