Scientists propose new ILUC analysis method

By Erin Voegele | November 06, 2012

A recently published research paper proposes the use of a new method to calculate land use change, referred to as baseline time accounting. The paper, titled “Baseline time accounting: Considering global land use dynamics when estimating the climate impact of indirect land use change caused by biofuels,” was authored by Jesper Kløverpris of Novozymes A/S and Steffen Mueller from the University of Illinois at Chicago. The article has been published in The International Journal of Life Cycle Assessment.

According to the researchers, indirect land use change (ILUC) models that aim to forecast the global warming impact of biofuel production generally incorporate time accounting in a simplistic way to allocate total carbon emitted from affected land to the volume of fuel that is produced. Kløverpris and Mueller argue that the accuracy of accounting for time in this type of model is severely limited by the use of the annualization approach, which requires arbitrary projections of future biofuels production. Land use emissions are allocated over this, but fail to incorporate actual land use dynamics, such as expanding and contracting agricultural land area.

The approach developed by Kløverpris and Mueller provides ILUC researchers with the ability to isolate the climate impact of biofuels-related land use changes from other land use changes.

"As many others, I have always been uncomfortable with the annualization method applied for time accounting in most previous ILUC studies because it is basically arbitrary," said Kløverpris. "A more sophisticated approach was required to assess the actual climate impact of indirect land use change. Baseline time accounting is our proposal for a more scientifically rigorous way of dealing with the time issue in ILUC studies as the science is refined."

According to information released on the study, most ILUC models assume a static land use baseline, even though land use trends differ regionally. More precise impacts are possible when ILUC emissions from conversions of the agricultural land are compared with emissions from the baseline conversion of the same land.

In addition, the new approach incorporates two types of land use dynamics not addressed in previously absent from ILUC models: accelerated expansion and delayed reversion. Accelerated expansion is where agricultural area is expanding. While biofuel production may cause land conversion to happen slightly sooner than it otherwise would, the researchers stress that the land would have likely come into production at some point anyway. Delayed reversion, alternatively, addresses ILUC in areas where farm land is taken out of production. In these areas biofuel production would likely slow the pace by which agricultural land is reduced.

When Kløverpris and Mueller applied this accounting method to two existing ILUC studies, the ILUC emissions predicted dropped by 60-70 percent.

In the paper, Kløverpris and Mueller state that several land use projections indicate that the global agricultural area will keep expanding up to, and beyond, 2050. “Our recommendation is therefore to apply the baseline time accounting concept as an integrated part of future ILUC studies and to update the results on a regular basis just as other estimations of carbon intensities are being updated,” they said in the report.