Greenhouse gas emissions and offset potential from sugarcane straw for bioenergy production in Brazil

Abstract

This study aims to assess the additional Greenhouse gas (GHG) emissions affected by straw removal from the soil surface in sugarcane areas, including measurement of short-term soil CO₂-C emissions plus emissions associated with the recovery and transport operations of straw bales until to the industry gate (diesel emissions) and estimated soil N₂O emission, comparing with leaving all straw on the soil surface. Taking into account the main sources evaluated (soil CO₂, diesel and N₂O from straw), the total additional GHG emissions from the recovery of 6.9 Mg Dry Matter ha^-1 (27%) was estimated at 1423 kg CO₂eq ha^-1, resulting in a carbon footprint of 206.2 kg CO₂eq per megagram (Mg) of straw recovered. Applying the parameters cited in this study for electricity generation (GHG emission and offset potential), our results showed an additional GHG emission of (+) 860 kg CO₂eq ha^-1. Applying the same parameters for second generation (2G) ethanol production replacing gasoline, an avoided GHG emission of (-) 2316 kg CO₂eq ha^-1 could be achieved. The route of recovering 27% of sugarcane straw from the soil surface through bale system for bioelectricity production using the technical parameters and industrial efficiency rate of this case study resulted in a C footprint of 347 kg CO₂eq MWh^-1. Improving the efficiency rate for straw conversion in bioelectricity based on its lower heating value could reduce its C footprint to 62.26 kg CO₂eq MWh^-1 produced. For sugarcane straw recovery at the first cutting cycle in clay soil, the option of producing ethanol 2G could offset GHG emissions once replacing fossil gasoline, resulting in a C footprint of 0.86 kg CO₂eq L^-1 of 2G ethanol in the agricultural phase, an option to contribute to better sustainability of sugarcane straw recovery, supporting renewable and sustainable bioenergy systems, and reducing the impacts of Global Climate Change.

Keywords

Biomass / renewable energy / soil management / harvest systems / climate change

References

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