Course: BFM 101 Biofuels Fundamentals

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Life Cycle Assessment
Life Cycle Assessment

Life Cycle Assessment (LCA) is a tool used to investigate and evaluate the environmental impacts of a product or service from “cradle-to-grave.” It is useful for tracking the sustainability of complex systems in a holistic manner. Another way to explain a Life Cycle Assessment is that it is a detailed analysis that calculates the energy and raw materials used to produce a particular product or process and the resulting release of pollutants into the air, water, and land.

The International Organization for Standardization (ISO) has prepared international standards that specify requirements and provide guidelines for LCA [1]. The ISO defines LCA as the “compilation and evaluation of the inputs, outputs and the potential environmental impacts of a product system throughout its life cycle.”

Figure 2. Life Cycle Assessment of biofuels includes all inputs and outputs along the supply chain.  US Department of Energy Biomass Program (http://www1.eere.energy.gov/biomass/)

What LCA Does

LCA is often used to compare energy and carbon balances for production and use of different fuels. As such, LCA is a key tool in assessing sustainability of biofuels. Currently, U.S. policy provides tax credits for companies that blend renewable fuels with petroleum-based fuels. In order to qualify for these credits, carbon dioxide emissions must be reduced by 40 percent for first-generation biofuels, and by 60 percent for second-generation biofuels, used in the blend. LCA is the tool used to determine the reduction or increase in emissions associated with production and use of each fuel type and therefore its acceptability for tax credits.

However, there is disagreement in the scientific and policy worlds as to what set of assumptions and variables to include in a life cycle assessment, particularly in regard to land use change. It is important to realize that an LCA is only as good as its data, and each LCA has its own set of assumptions that must be understood.

Most people would agree that any new alternative fuel should achieve greater environmental benefit than conventional fuels and should yield higher net energy than was used to produce the fuel. The measurement used is the fossil energy ratio which is the relationship between "the fossil energy used to produce the crop" to "the bioenergy derived from the crop".

Direct Land Use Change

Direct land use change is when a farmer or land owner decides to grow an energy crop where no other crop was grown previously, or where a non-energy crop (food, fiber, or feed) was grown. An example of direct land use change is when a farmer converts forest, fallow, or cropland, or takes land out of the Conservation Reserve Program (CRP), to grow a bioenergy crop.

Indirect land use change

Indirect land use change occurs when there is a reduction in the supply of a crop in one country or region, causing another country or region to increase production of that crop. Usually land is diverted from other uses to achieve this. In many cases, forested land is converted to crop production.  When forested land is cleared for agricultural production, huge amounts of CO2 are released into the atmosphere.

U.S. energy policy has encouraged the conversion of corn grain to ethanol. In 2002, almost one billion bushels (9 percent) of U.S. corn were converted to ethanol. By 2010, this number swelled to 4.5 billion bushels (31 percent). The indirect land use theory states that if the demand has not changed, someone else will need to produce the 3.5 billion bushels of corn that have been diverted to the new ethanol market.

When indirect land use change is included in the LCA to evaluate the greenhouse gas effects of bioenergy crop production, it will have a significant impact on the results. One investigator might argue that bioenergy crop production in one region could lead to deforestation in another region, while another investigator might conclude that forest would be cleared anyway for other reasons. The decision whether to include indirect land use change in the LCA is the subject of much discussion among scientists and policy makers.

An Important Tool, BUT…

LCA is a very useful tool in evaluating a particular process or product. But, it is important to realize that an LCA is only as good as its data, and each LCA has its own set of assumptions that must be considered and understood. Therefore, it is difficult to compare different life cycles with one another.

Scientists and policy makers will continue to debate the issue of indirect land use change and whether it should be part of our federal renewable energy policies. When you read LCA results make sure you fully understand the data and the assumptions stated.

Related articles

- Life Cycle Assessment

This bulletin from West Virginia University Extension provides overview materials and diagrams of how life cycle analysis is conducted, but is not specific to bioenergy.

Resources provided by the eXtension Farm Energy Community of Practice at http://www.extension.org/ag+energy

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Sustainable Management for Biomass Production