**6. Life cycle analysis of energy, emissions and GHG for DME fuel**

Life cycle studies are used to compare the effect of different fuels/energy sources/ transport technologies. Life-cycle analysis consists of Well-to-Pump (WTP) and Pumpto-Wheel (PTW) estimation of energy consumption and emission of pollutants and GHG impact of these pollutions. WTP path consists of a) recovery and transport of raw material, b) production of the fuel, c) transportation of fuel, and d) distribution. PTW is the vehicle operation part of the pathway. **Figure 13** shows a schematic to illustrate the Well-to-Wheel cycle for different fuel/transport technology combinations.

Many studies on life cycle energy consumption and emissions for DME fuel have been carried out globally. Lee et al. have investigated Well-to-Wheels emissions of greenhouse gases and air pollutants of di-methyl ether from natural gas and renewable feedstocks in comparison with petroleum gasoline and diesel in the United States and Europe. For this purpose they have used Greenhouse gases, Regulated Emissions and Energy use in Transportation (GREET) model developed by Argonne National Laboratory (ANL). They have used five pathways to calculate the WTW by use of DME as fuel, these are 1) fossil NG with large-scale DME plants, 2) methanol from fossil NG with large-scale plants for both methanol and DME (separately), 3) land-fill-gas (LFG) with small-scale DME plants, 4) manure-based biogas with small-scale DME plants, 5) methanol from black liquor gasification with small-scale DME plants. They

*Replacement of Diesel Fuel by DME in Compression Ignition Engines: Case for India DOI: http://dx.doi.org/10.5772/intechopen.104969*


#### **Table 7.**

*Global development of DME engines [12, 18].*

have studied DME production and use in the US and Europe in two class of vehicles (light-duty (LDV) and heavy-duty vehicles (HDV). Their studies show that WTW consumption of fossil energy and emission of GHG emissions in production and use of DME fuel is very low as compared to diesel and gasoline vehicles. Five pathways used in the production of DME are shown in **Figure 14**.

In this study a small DME production plant is assumed to have a capacity of 25 MTPD (metric ton per day) and a large-scale plant is one with a capacity of 3600 MTPD. Case NG uses the fossil NG to produce DME directly in a large scale DME production plant. NG is supplied to the DME production plant through a pipeline. In case MeOH fossil NG is first converted to methanol and thence to DME. In this case


**Figure 14.**

```
Five pathways for production of DME [20].
```
the methanol production plant is close to the source of NG and methanol is transported to the DME production units by rail. Biogas from two sources has been considered, i.e., a) landfill gas (LFG) and b) during production and treatment of manure (MANR). Both are taken as renewable alternatives. Biogas is made up of CH4 and CO2 and is generated by anaerobic digestion (AD) of organic wastes. In both cases DME plant are small scale plants co-located with the source of biogas. Before the biogas can be fed into the DME plant it has to be cleaned in separate reactors where impurities like Sulfur compounds etc. are removed and the biogas is upgraded to the required composition.

*Replacement of Diesel Fuel by DME in Compression Ignition Engines: Case for India DOI: http://dx.doi.org/10.5772/intechopen.104969*

**Figure 15.**

*WTW energy consumption and emissions for DME produced through different pathways. (a) Comparison of WTW energy consumption for DME production vis-a-vis gasoline and diesel production in US and EU [20]. (b) WTW GHG emissions from DME production as compared to diesel and gasoline for US and EU [20].*

**Figure 15(a)** depicts the WTW energy consumption for DME production through different pathways. DME production seems to consume more energy per MJ of fuel produced as compared to gasoline and diesel in both US and EU. This is because the conversion efficiency of raw material to DME is significantly lesser than gasoline and diesel. Although, conversion of fossil NG to DME directly or through MeOH is lesser than gasoline and diesel, however, this may also be due to scale of operation and size of plants which are much bigger and established for gasoline and diesel. Also, production of DME from renewable sources will result in zero or negligible consumption of fossil fuel.

**Figure 15(b)** shows the GHG emissions from DME production gasoline and diesel consumption and MeOH production. The emissions consist of the following components, a) For preparation and transportation of feedstock, b) Production of fuel and its transport, c) Avoided combustion and non-combustion emissions, d) biogenic CO2 in fuel and e) Fuel combustion. In the case of DME produced from bio-gas, avoided combustion and non-combustion are a major portion of the emissions inventory and in reducing the WTW emissions to very low/negative values. Thus, WTG GHG for LFG and manure based bio-gas are 6 and 1 gCO2 e/MJ respectively and are 93% and 101% lower than US diesel. In the EU LFG and manure based bio-gas to DME process shows 6 and 12 gCO2 e/MJ of GHG emissions respectively which are 92% and 87% lower than EU diesel. If, however, regional electricity is used for production of DME then the WTW GHG emissions in the US will increase to 25 and 1 gCO2 e/MJ for LFG and manure bio-gas respectively. In the EU, the corresponding figures for DME production are 19 and 13 gCO2e/MJ from LFG and manure biogas respectively. Thus, it can be seen that the energy mix of the process has a strong impact on the WTW emissions as well.

In **Figure 16**, WTW GHG emissions vs. WTW vehicle energy consumption are plotted for some alternative fuels and petroleum-based gasoline and diesel. **Figure 17** plots the results for synthetic diesel from farmed wood, synthetic diesel from waste

**Figure 16.** *Well-to-wheel GHG emissions & vehicle energy consumption for some alternate fuels [18].*

#### **Figure 17.**

*Different type of coal gasifiers [21]. (a) Moving Bed Gasifier concept. (b) Fluidized Bed Gasifier concept. (c) Entrained Flow Gasifier concept.*

wood and black liquor, ethanol from sugarcane (Brazil) and DME from waste wood and black liquor. WTW GHG emissions of DME produced from waste wood and black liquor are the lowest of all the fuels studied. WTW energy consumption (MJ/100 Km) for DME is second lowest after petroleum fuels. This may be due to the established production process of petroleum fuels and well-optimized engine and vehicle technologies for petroleum-based fuels. It is possible the life cycle energy consumption of DME fuel will reduce as the production technology for DME is matured and CIDI engines are designed specifically for DME fuel.

*Replacement of Diesel Fuel by DME in Compression Ignition Engines: Case for India DOI: http://dx.doi.org/10.5772/intechopen.104969*
