Climate effect of an integrated wheat production and bioenergy system with Low Temperature Circulating Fluidized Bed gasifier. (15th December 2015)

• Record Type: Journal Article
• Authors: Sigurjonsson, Hafthor Ægir; Elmegaard, Brian; Clausen, Lasse Røngaard; Ahrenfeldt, Jesper
• Is Part Of: Applied energy. Volume 160(2015:Dec. 15)
• Page Start: 511
• Page End: 520
• Publication Date: 2015-12-15
• Subjects: Life Cycle Assessment -- Wheat production -- Straw utilization -- Thermal gasification -- Carbon soil sequestration; Power (Mechanics) -- Periodicals; Energy conservation -- Periodicals; Energy conversion -- Periodicals; 621.042
• DOI: 10.1016/j.apenergy.2015.08.114
• Languages: English
• ISSNs: 0306-2619

Abstract

Highlights: Wheat straw removal from agricultural system has considerable GWP effect. Changing the carbon conv. in the gasifier to 0.8–0.86 mitigates those effects. Considerable difference is between sequestration potential of straw and biochar. Lowering the carbon conversion improves GWP, but depends on subst. technology. Abstract: When removing biomass residues from the agriculture for bioenergy utilization, the nutrients and carbon stored within these "residual resources" are removed as-well. To mitigate these issues the energy industry must try to conserve and not destroy the nutrients. The paper analyses a novel integration between the agricultural system and the energy system through the Low Temperature Circulating Fluidized Bed (LT-CFB) gasifier from the perspective of wheat grain production and electricity generation using wheat straw, where the effects of removing the straw from the agricultural system are assessed along with the effects of recycling the nutrients and carbon back to the agricultural system. The methods used to assess the integration was Life Cycle Assessment (LCA) with IPCC's 2013 100 year global warming potential (GWP) as impact assessment method. The boundary was set from cradle to gate with two different functional units, kg grain and kW h electricity produced in Zealand, Denmark. Two cases were used in the analysis: 1. nutrient balances are regulated by mineral fertilization and 2. the nutrient balances are regulated by yield. The analysis compare three scenarios of gasifier operation based on carbon conversion to two references, no straw removal and straw combustion. The results show that the climate effect of removing the straws are mitigated by the carbon soil sequestration with biochar, and electricity and district heat substitution. Maximum biochar production outperforms maximum heat and power generation for most substituted electricity and district heating scenarios. Irrespective of the substituted technologies, the carbon conversion needs to be 80–86% to fully mitigate the effects of removing the straws from the agricultural system. This concludes that compromising on energy efficiency for biochar production can be beneficial in terms of climate change effect of an integrated wheat production and bioenergy system.