**6. Results and discussion**

By reason of space, the safety checklist only reports the most important bullet points referred to as the three examined hazards (**Tables 3–5**).

The safety checklist for the biogas industry can support the hazards identification and the definition of the prevention and protection measures and, if used in the right way, forms a basic part of risk assessment. It is essential that the checklist is used as a means of development

#### **Biohazard assessment**

Are there operations/tasks, which may result in bioaerosol, organic dust or particulate dispersion (biomass reception, its storage, grinding, shredding or other pre-processes of the biomass, digester loading operations, digestion drainage, sampling activity or maintenance work)?

Are high-exposure activities performed within indoor places?

Are the work processes designed to reduce the releases of organic dust and bioaerosol in the workplace?

Is the biomass stored in closed containers/tanks?

Are there leakages of solids or leachate during the handling phases of the materials entering and leaving the system?

Do workers have direct contact with manure, slurry or other organic waste?

Are there risks of splashes and spills contaminated with biological agents?

Are workers particularly subject to the risk of infective or immunological diseases (workers with particular allergies or asthma, low immune system, pregnant women)?

#### **Prevention and protection measures**

In indoor places, are collective protection measures applied to the source of the biohazard, such as ventilation systems and appropriate work organization procedures?

Is the workplace regularly cleaned? Are operating procedures defined?

Is the **workplace** provided with hand-washing and shower facilities and 'clean areas'?

Is eating and drinking forbidden in the workplace?

Are warning and safety signs used at the workplace? Do workers have difficulty of national language understanding?

Do workers receive information on biohazards and protective measures before assuming their tasks?

Are vehicles, circulating in the biogas plant, subjected to regular washing?

Is the vehicle cab equipped with dedicated ventilation systems? Is the monitoring of the door seals and the filter maintenance provided?

Are workers provided with respiratory protective equipment (RPE) during high-exposure activities?

Do workers carry out trainings focused on the right use of individual protection devices?

Is it verified that the defined procedures are actually observed by the workers?

Are workers under health surveillance?

Are workers informed of the significance of health assessments and their outcomes?

Is there a system which reports the accidents and records the episodes of contamination with biological agents (even mild)?

Are workers aware of the importance of recording any contamination episodes?

**Table 3.** 'Safety checklist' extract: biohazard.

#### **Explosion risk**

**Biohazard assessment**

**5. Fire risk**

194 Advances in Biofuels and Bioenergy

drainage, sampling activity or maintenance work)?

**6. Results and discussion**

Is the biomass stored in closed containers/tanks?

or asthma, low immune system, pregnant women)?

Is eating and drinking forbidden in the workplace?

systems and appropriate work organization procedures?

Is the workplace regularly cleaned? Are operating procedures defined?

Are vehicles, circulating in the biogas plant, subjected to regular washing?

Is the **workplace** provided with hand-washing and shower facilities and 'clean areas'?

**Prevention and protection measures**

understanding?

Are high-exposure activities performed within indoor places?

to as the three examined hazards (**Tables 3–5**).

Do workers have direct contact with manure, slurry or other organic waste? Are there risks of splashes and spills contaminated with biological agents?

Are there operations/tasks, which may result in bioaerosol, organic dust or particulate dispersion (biomass reception, its storage, grinding, shredding or other pre-processes of the biomass, digester loading operations, digestion

By reason of space, the safety checklist only reports the most important bullet points referred

The safety checklist for the biogas industry can support the hazards identification and the definition of the prevention and protection measures and, if used in the right way, forms a basic part of risk assessment. It is essential that the checklist is used as a means of development

In order to reduce the fire risk, the safety checklist suggests several recommendations and actions, which consist of prevention, protection and managerial measures. By reason of space, the checklist only shows the most important points related to fire risk. In order to minimize the fire effects, biogas production plant has to be divided into fire protection sectors [29], for example, the anaerobic digester, the biogas holder and CHP unit. Certain distances must be maintained among these sectors. In particular, during the biogas holder construction, specific safety distances must be ensured (internal and external safety distance and protection distance).

Are there leakages of solids or leachate during the handling phases of the materials entering and leaving the system?

Are workers particularly subject to the risk of infective or immunological diseases (workers with particular allergies

In indoor places, are collective protection measures applied to the source of the biohazard, such as ventilation

Are warning and safety signs used at the workplace? Do workers have difficulty of national language

Do workers receive information on biohazards and protective measures before assuming their tasks?

Are the work processes designed to reduce the releases of organic dust and bioaerosol in the workplace?

#### **Prevention measures**

Are places with explosion risk classified into zones (0, 1 and 2) according to the probability of occurrence of potentially explosive atmosphere?

Are hazardous zones (0, 1 and 2) characterized in terms of volume and extent?

Is persistence time of explosive atmosphere calculated?

Are suitable ventilation rates ensured in indoor places in order to dilute biogas concentration below lower explosive limit?

Are standby fans or an emergency ventilation system installed in indoor workplaces (container of CHP unit)?

Are there adequate openings aimed at ensuring a good natural ventilation in indoor workplaces?

Are wind action and stack effect taken into account for dimensioning the openings of indoor workplaces (natural ventilation)?

Are work equipments and protective devices selected on the basis of categories set out in Directive 2014/34/EU?

Is all process control equipment classified according to European Standards?

Is the air flow, injected for biological desulphurization, matched with the current rate of biogas production (max. 6% volume)?

#### **Protection measures**

Can a biogas release be diverted **or** removed to a safe place or, if that is not practicable, safely contained by other suitable methods?

Are flame arresters installed in biogas pipes?

Are **biogas holders** equipped with positive (hydraulic seal) and negative pressure protection devices?

Is the water filling of pressure safety devices daily controlled and is the correct water level maintained?

Are all closed tanks, in which fermentation can occur, provided with pressure safety devices?

#### **Managerial measures**

Are workers equipped with working clothes which do not generate electrostatic charges?

#### **Explosion risk**

Are hazardous areas indicated by specific signals?

Is there an obligatory journal **for the documentation** of all daily measurements, controls and maintenance works as well as failures?

Is there a plan indicating the explosion protection zones?

Is it certain that an operational manual is available before any work is done?

Is it established in the manual that safety devices have to be checked at least once a week and after any failure?

Is the engine (CHP unit) maintained according to the timetable given by the manufacturer?

Is the CHP unit maintained or checked by specialized companies?

Are all parts of the biogas plant, containing a gas flow, regularly checked and submitted to a pressure test at least every year?

Are operating instructions readily available, easy to see and read by the operators during their work?

Is artificial ventilation system of container, which includes CHP unit, maintained and checked according to the timetable given by the manufacturer and if necessary is it maintained or checked by specialized companies?

> support and not simply as a 'tick off-the-box' exercise. A specific sector guidance, referred to the potential risks to biogas plants workers health and their assessment and management, is required, and it is likely that site operators will be in need of specialist advice to carry out an effective risk assessment and develop risk control procedures. In this context, the reported checklist can improve the safety culture in the biogas field. In conclusion, it has to be stressed that the safety checklist has been tested in some biogas production plants, where inspections

> Countries of the European Union (EU) have agreed on a new 2030 Framework for climate and energy, which includes targets and policy objectives for the period between 2020 and 2030. These targets are aimed at achieving a more competitive, secure and sustainable energy system. A specific target has established that at least a 27% share of renewable energy consumption must be achieved. In this context, biogas/biomethane production plants can be strategic, and therefore particular attention has to be paid for their safe operation. In fact, biogas industry is experiencing fast growth worldwide. However, the number of accidents in biogas production is growing even faster. The estimated risk profile of biogas production confirmed that its production process presents a non-negligible risk. Accident analysis can improve the safety of such plants. In particular, creation of an accidents report can be strategic in order to individualize the more hazardous operations and elements which require a specific maintenance schedule. Indeed the decrease of number of accidents, which occurred in the biogas production plants, could be easily achieved by adapting the process safety experience acquired in other industrial sectors. With regard to this topic, it is important to remember that the typical culture of the farming is far enough from industrial approach and therefore it requires clear and useful tools, which are able to address both elements—maintenance and operation. The safety checklist can meet these requirements, because it is a practical tool, which can be used

and audit activities were simulated in order to verify its real feasibility.

Are smoking, naked flames and storage of flammable materials forbidden in the plant area?

Are maintenance operations reported in a specific register? Is electrical equipment maintenance regularly carried out?

cutting, etc.), which involve a fire risk, are carried out?

Are firefighting systems periodically checked? Are gas sensors/fire detectors periodically checked?

**Table 5.** 'Safety checklist' extract: fire risk.

Are there adequate and well-marked routes for fire brigade vehicles?

Is firefighting system maintenance regularly carried out in accordance with the reported directions?

Are fire protection posts set up and suitable fire extinguishers made available when works (welding, abrasive

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Is it certain that the operation and maintenance of biogas plant is done by reliable and qualified persons?

**7. Conclusions**

**Fire risk**

**Table 4.** 'Safety checklist' extract: explosion risk.

#### **Fire risk**

#### **Prevention measures**

Are biogas holder membranes made of fire-resistant materials?

Do biogas holder membranes avoid the formation of electrostatic charges?

Are electrical equipments designed in accordance with Regulations and Technical Standards?

Are electrical equipments provided with protective grounding?

Are biogas holders protected from lightning?

Is the storage of flammable materials, flammable liquids and gases limited to small amounts?

#### **Protection measures**

Are biogas pipes insulated to give protection against fire and provided with fire protection flaps?

Is the protection distance respected during the biogas holder placing?

Is the internal safety distance respected during the biogas holder placing?

Is the external safety distance respected during the biogas holder placing?

Are there enough fire extinguishers on plant site?

Are there gas/fire detectors, which sound an alarm in case of fire?

Are the hydrants chosen in accordance with Technical Standards in terms of flow and pressure?

Is an additional generator, aimed at ensuring electric delivery in case of failures, installed?

#### **Managerial measures**

Is a responsible person designated for all fire protection measures?

Are fire protection exercises regularly carried out?

#### **Fire risk**

Are smoking, naked flames and storage of flammable materials forbidden in the plant area? Is firefighting system maintenance regularly carried out in accordance with the reported directions? Are maintenance operations reported in a specific register? Is electrical equipment maintenance regularly carried out? Are there adequate and well-marked routes for fire brigade vehicles? Are fire protection posts set up and suitable fire extinguishers made available when works (welding, abrasive cutting, etc.), which involve a fire risk, are carried out? Are firefighting systems periodically checked? Are gas sensors/fire detectors periodically checked? Is it certain that the operation and maintenance of biogas plant is done by reliable and qualified persons?

**Table 5.** 'Safety checklist' extract: fire risk.

support and not simply as a 'tick off-the-box' exercise. A specific sector guidance, referred to the potential risks to biogas plants workers health and their assessment and management, is required, and it is likely that site operators will be in need of specialist advice to carry out an effective risk assessment and develop risk control procedures. In this context, the reported checklist can improve the safety culture in the biogas field. In conclusion, it has to be stressed that the safety checklist has been tested in some biogas production plants, where inspections and audit activities were simulated in order to verify its real feasibility.

#### **7. Conclusions**

**Fire risk**

every year?

**Explosion risk**

196 Advances in Biofuels and Bioenergy

well as failures?

Are hazardous areas indicated by specific signals?

Is there a plan indicating the explosion protection zones?

Is it certain that an operational manual is available before any work is done?

Is the CHP unit maintained or checked by specialized companies?

Is the engine (CHP unit) maintained according to the timetable given by the manufacturer?

**Prevention measures**

**Protection measures**

**Managerial measures**

Are biogas holder membranes made of fire-resistant materials?

Are electrical equipments provided with protective grounding?

Is the protection distance respected during the biogas holder placing? Is the internal safety distance respected during the biogas holder placing? Is the external safety distance respected during the biogas holder placing?

Are there gas/fire detectors, which sound an alarm in case of fire?

Is a responsible person designated for all fire protection measures?

Are biogas holders protected from lightning?

**Table 4.** 'Safety checklist' extract: explosion risk.

Are there enough fire extinguishers on plant site?

Are fire protection exercises regularly carried out?

Do biogas holder membranes avoid the formation of electrostatic charges?

Are electrical equipments designed in accordance with Regulations and Technical Standards?

Is there an obligatory journal **for the documentation** of all daily measurements, controls and maintenance works as

Is it established in the manual that safety devices have to be checked at least once a week and after any failure?

Are all parts of the biogas plant, containing a gas flow, regularly checked and submitted to a pressure test at least

Is artificial ventilation system of container, which includes CHP unit, maintained and checked according to the timetable given by the manufacturer and if necessary is it maintained or checked by specialized companies?

Are operating instructions readily available, easy to see and read by the operators during their work?

Is the storage of flammable materials, flammable liquids and gases limited to small amounts?

Are biogas pipes insulated to give protection against fire and provided with fire protection flaps?

Are the hydrants chosen in accordance with Technical Standards in terms of flow and pressure? Is an additional generator, aimed at ensuring electric delivery in case of failures, installed?

Countries of the European Union (EU) have agreed on a new 2030 Framework for climate and energy, which includes targets and policy objectives for the period between 2020 and 2030. These targets are aimed at achieving a more competitive, secure and sustainable energy system. A specific target has established that at least a 27% share of renewable energy consumption must be achieved. In this context, biogas/biomethane production plants can be strategic, and therefore particular attention has to be paid for their safe operation. In fact, biogas industry is experiencing fast growth worldwide. However, the number of accidents in biogas production is growing even faster. The estimated risk profile of biogas production confirmed that its production process presents a non-negligible risk. Accident analysis can improve the safety of such plants. In particular, creation of an accidents report can be strategic in order to individualize the more hazardous operations and elements which require a specific maintenance schedule. Indeed the decrease of number of accidents, which occurred in the biogas production plants, could be easily achieved by adapting the process safety experience acquired in other industrial sectors. With regard to this topic, it is important to remember that the typical culture of the farming is far enough from industrial approach and therefore it requires clear and useful tools, which are able to address both elements—maintenance and operation. The safety checklist can meet these requirements, because it is a practical tool, which can be used to carry out the analysis of hazards of biogas plants. Starting from a scientific analysis of preventive and protective measures, the checklist has been designed to assess the actual safety levels of the biogas plant and to support the operators in order to improve the safe process management. Furthermore, the development and application of specific safety standards to the biogas sector would be beneficial to avoid design and operational errors.

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