Biodiesel Greenhouse Gas Emissions
Lifecycle analysis, sometimes referred to as fuel cycle or well-to-wheel analysis, is used to assess the overall greenhouse gas (GHG) impacts of a fuel, including each stage of its production and use. EPA’s lifecycle analysis includes significant indirect emissions as required by the Clean Air Act.EPA's lifecycle analysis for the Renewable Fuel Standard (RFS) includes emissions related to:.The sum of all of these lifecycle emissions for each renewable fuel pathway are then compared to the direct emissions from the baseline petroleum fuel it displaces. The results of these analyses are used to determine if the fuel pathways meet the GHG reduction thresholds required by the CAA.
Table of Contents. Biofuels and the Carbon Cycle. Indirect Land Use Impacts of Biofuels. Differences among Biofuels. Biofuels and the Carbon Cycle. From the standpoint of human-released carbon dioxide, other greenhouse gas emissions, and contributions to climate change biofuels have one large advantage over gasoline, diesel and other fossil fuels: The feedstocks for biofuels are part of the.
Feedstock Production and Transportion. EPA's analysis of feedstock production considers the domestic and international agricultural/forestry sector-wide impacts of biofuels. The fuel production stage of the analysis includes the GHG emissions associated with a specific type of fuel production technology, including all of the energy and material inputs used in the fuel production process and the impacts of any co-products.This includes energy and material inputs used for handling, processing, and storing the feedstocks, co-products, intermediate products, and resulting fuel. The GHG emissions are calculated using emissions factors for all of the process energy (e.g., natural gas, coal) and electricity used for fuel production operations. These factors include the upstream emissions associated with extraction, transport, and distribution of the energy, and are generally determined on an average basis (e.g., grid average electricity in the United States).
The upstream emissions associated with significant material inputs used to produce the renewable fuel, such as methanol for biodiesel production, are also included.The EPA's assessment of fuel production does not include activities that are clearly unrelated to the fuel lifecycle (e.g., offset projects) or emissions associated with physical and organizational infrastructure (e.g., facility construction, employees commuting to the facility).EPA’s analysis also includes the emissions associated with distributing the finished fuel to the consumer.Co-products. Co-products that are used in the agricultural sector are included in EPA's modeling of the global agricultural and forestry sector. Other co-products are evaluated by considering the emissions impacts of their most likely uses and the products they displace in the market. In general, this co-product analysis applies globally, meaning any GHG emissions associated with co-product use are included. EPA has limited capacity to draw distinctions among different fuel producers based on slight modifications in how their co-products are used.
These slight variations are not likely to have a significant impact on the emissions analysis, as the average impacts on the overall market will tend to be similar regardless.
.Production and use of jatropha biodiesel in Tanzania result into positive net greenhouse gas (GHG) emissions.The net GHG emission is highly influenced by end use of biodiesel in a diesel engine followed by soil N 2O emissions during farming of Jatropha.Jatropha biodiesel results into significant net energy gain; however its production requires large quantity of fossil energy input.Biodiesel conversion found to be a major energy consuming process followed by jatropha farming.The results of the study are meant to inform stakeholders and policy makers in the bioenergy sector. This paper evaluates GHG emissions and energy balances (i.e.
California Greenhouse Gas Emissions
Net energy value (NEV), net renewable energy value (NREV) and net energy ratio (NER)) of jatropha biodiesel as an alternative fuel in Tanzania by using life cycle assessment (LCA) approach. The functional unit (FU) was defined as 1 tonne (t) of combusted jatropha biodiesel. The findings of the study prove wrong the notion that biofuels are carbon neutral, thus can mitigate climate change. A net GHG equivalent emission of about 848 kg t −1 was observed. The processes which account significantly to GHG emissions are the end use of biodiesel (about 82%) followed by farming of jatropha for about 13%. Sensitivity analysis indicates that replacing diesel with biodiesel in irrigation of jatropha farms decreases the net GHG emissions by 7.7% while avoiding irrigation may reduce net GHG emissions by 12%. About 22.0 GJ of energy is consumed to produce 1 t of biodiesel.
Biodiesel conversion found to be a major energy consuming process (about 64.7%) followed by jatropha farming for about 30.4% of total energy. The NEV is 19.2 GJ t −1, indicating significant energy gain of jatropha biodiesel. The NREV is 23.1 GJ t −1 while NER is 2.3; the two values indicate that large amount of fossil energy is used to produce biodiesel.
The results of the study are meant to inform stakeholders and policy makers in the bioenergy sector. Previous article in issue. Next article in issue.