Conducting in-depth life-cycle assessments of the environmental impacts of biofuels is complicated, and new research suggests some questions in comparing biofuels to alternatives like petroleum-based fuels will never be answered.
Furthermore, one study argues, consumer choices driven by price differences between bio-based and petroleum-based fuels will play into how biofuels affect the environment, adding another layer of complication that must considered.
The two papers were recently published by the Energy Biosciences Institute, a partnership among oil giant BP PLC; the University of California, Berkeley; the University of Illinois, Urbana-Champaign; and the Lawrence Berkeley National Laboratory.
In a paper titled "Grand Challenges for Life-Cycle Assessment of Biofuels," lead author Thomas McKone, an expert on health risk assessments with the Berkeley Lab and the University of California, Berkeley, describes major obstacles in completing life-cycle assessments for biofuels.
Those assessments, which aim to put concrete numbers behind the raw materials extraction, manufacturing, distribution, use and disposal of biofuels, are key decision tools for policies like the federal renewable fuel standard and California's low-carbon fuel standard.
Biofuels stakeholders debate the elements that should be included in such life-cycle assessments, in part due to remaining uncertainties in the science and data behind different technology choices.
The researchers describe tension in developing life-cycle assessment tools between moving fast to facilitate industry development, and moving carefully.
"We need technology momentum, but we must simultaneously maintain options for adaptive decision-making" to avoid sunk costs in the wrong choices, they write.
And they warn in a description of what many consider to be a political reality in Washington, "once a commitment is made to adopt ethanol, even if it is considered a 'bridge' or short-term option, technology momentum will impede opportunities to move to any other alternative."
Short list of challenges, long list of problems
McKone and his colleagues boil the key challenges to conducting biofuels life-cycle assessments down to seven points:
- Understanding how farmers make decisions about feedstocks and land use.
- Predicting how biofuel production technologies will evolve.
- Characterizing tailpipe-emission changes from biofuels and their health consequences.
- Accounting for geographic variables in how particular choices play out.
- Deciding on the appropriate time scales to consider.
- Assessing transitional impacts as biofuels are adopted.
- Managing uncertainty.
But those categories roll up a much longer list of problems detailed in the paper.
In the first category, for example, understanding farmer decisionmaking is complicated by the hundreds or thousands of actors whose individual decisions will relate to their own land characteristics, costs and existing investments, among other factors, the authors say.
Designing policies around life-cycle analyses that can drive the decisions of those farmers is very different from designing policies to change behavior among the relatively few, powerful companies involved in the petroleum business, they say.
Highlighting an inherent tension between the work of scientists like those at the Energy Biosciences Institute, regulators, and the inventors and entrepreneurs on the ground, the paper says life-cycle assessments are most informative when they are based on data gathered from technology deployment, rather than as a policy development tool to steer development choices.
As a result, the analysis says, it is "difficult to apply [life-cycle assessments] during the early phases of a major technology shift."
Not a 1-to-1 replacement
Adding another layer of complexity to life-cycle assessments, a second recent paper funded by the same public-private group argues for the inclusion of a new, market-mediated factor in biofuels life-cycle assessments.
In "Indirect Fuel Use Change (IFUC) and the Lifecycle Environmental Impact of Biofuel Policies," Deepak Rajagopal, a researcher at the University of California, Los Angeles' Institute of the Environment and Sustainability, and colleagues take issue with the common assumption that biofuels will replace fossil fuel use on a 1-to-1 basis.
"The adoption of renewable fuels will affect the price of fuel and therefore affect total fuel consumption, which may increase or decrease depending on the policy regime and market conditions," the authors explain.
"Assuming biofuels are costlier than fossil fuels, a domestic biofuel mandate such as the US Renewable Fuel Standard is likely to raise domestic fuel price and lower domestic fuel consumption. ... At the same time, by reducing the demand for fossil fuels, domestic policies lower the international price of fossil fuels and [cause] an increase in fossil fuel consumption in the rest-of-the world," they say.
The researchers' larger point, beyond advocating for the inclusion of fuel use change in life-cycle assessments, is that if such analyses are going to include indirect effects stemming not from the fuel's supply chain but from related system changes, then a much wider field of such effects must be considered.
An active debate among biofuels stakeholders addresses whether "indirect land-use change," or changes in land usage from increasing agricultural demand triggered by biofuels markets, should be taken into account in tallying their emissions.
The science and economics of modeling those effects are still emerging, leading some advocates to say it is too early -- or simply inappropriate -- to include indirect land-use change in biofuels emissions accounting. Both the federal government and the state of California, however, have committed to incorporating that factor into their biofuels policies.
Addressing the findings of the two papers, Geoff Cooper, vice president of research and analysis for the corn ethanol group Renewable Fuels Association, said they echo arguments the organization has made before.
"These papers confirm that while life-cycle assessment can provide important insight, there remains tremendous uncertainty around the results, wide knowledge gaps, inconsistent system boundaries, and substantial differences in analytical approaches," he said.
"These papers underscore our concerns about the use of life-cycle analysis as a rigid regulatory tool," he added. "While life-cycle analysis tools can be instructive to the policy or regulatory development process, their results cannot and should not be interpreted as the gospel truth about the real-world impacts of a particular energy system."
Cooper said the second paper, in particular, reflects a position long held by the group.
"If we're going [to] scrutinize indirect land-use change for biofuels, intellectual honesty requires that we look at the universe of other potential indirect effects for other fuels -- both positive and negative -- with the same level of scrutiny," he said.