What is it about?

Feedstock-based biofuels require a substantial land base supporting agricultural activities. The growing need to replace oil and gas-based fuels in industrialised countries has increased the demand for crop-based biofuels generated from tropical agricultural land. This 2008 study explored the ecosystem ‘carbon payback time’ (ECPT) (the time needed to avoid fossil fuel emissions from biofuels to offset the losses in ecosystem carbon stocks during land conversion) in specific regions of tropics. For this, the authors used a geographically detailed crop database that includes locations and yields of crops, accounts of vegetation, and soil biomass estimates.

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Why is it important?

Clearance of forests and their conversion to agricultural lands deplete the enormous carbon storage of tropical woodland ecosystems. Therefore, using crop-based biofuels as an alternative to fossil fuels presents a critical environmental paradox: using feedstock-based biofuels can lead to a net reduction of greenhouse gases only if expanding the agricultural land for crop production does not come at the ecological price of deforestation. The study showed that expanding the present biofuel generation from all feedstock crops by clearing the natural ecosystem would require 30–300 years for carbon payback - an unacceptably long time for any reasonable carbon mitigation efforts. The authors, therefore, suggest a more sustainable solution for achieving substantial carbon benefits by expanding high-yielding crops, such as sugarcane and oil palm, into already degraded or cultivated lands. KEY TAKEAWAY: As the future global need for food and feed already poses a tremendous threat to tropical forests, policymakers should focus on alternative biofuel expansion pathways that do not require deforestation and reward efforts to protect the forests instead.

Read the Original

This page is a summary of: Carbon payback times for crop-based biofuel expansion in the tropics: the effects of changing yield and technology, Environmental Research Letters, July 2008, Institute of Physics Publishing,
DOI: 10.1088/1748-9326/3/3/034001.
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