Sustainability assessment of agro-bioenergy systems is often done without accounting for most of the associated sustainability challenges (e.g. food security, energy security, biodiversity conservation, fresh water depletion-consumption and pollution, greenhouse gas emission reduction and climate change mitigation etc.) within a single frame. In response to this, this study explored the possibility of applying a combination of the human appropriation of net primary production (HANPP) framework and life cycle assessment (LCA) based frameworks (namely the energy return on energy invested (EROEI), greenhouse gas balance (GHG) and water footprint (WF) frameworks) for sustainability assessment of agro-bioenergy systems across three broad agro-ecological zones (namely tropics-Latitude 0-23.5° N and S, sub-tropics- Latitude 23.6-40° N and S and temperate- Latitude 40.1 -60° N and S), over three future time scales (namely 2030, 2050 and 2070), using maize ethanol and biogas production systems as case studies, and biomass, energy, carbon and water flows per hectare as reference units.
While the HANPP framework accounts for the biophysical and socioeconomic flows of biomass from nature to society, the LCA based EROEI, GHG, and WF frameworks accounts for the energy, GHG, and water flows involved in the energetic appropriation of the three different HANPP components relevant for agro-bioenergy production (namely the harvested grain (HG), the extracted residue (ER) and the unextracted residue (UnE)). The energetic use of HG is a relevant sustainability subject because it competes directly with food supply chains, hence its connections to food security. The energetic use of ER is important because it opens sustainability discussions on pathways for more efficient and cascade use (i.e. reuse) of biomass especially within the context of global transition to bio-economy. The energetic use of UnE is also very essential because of its purported availability for meeting emerging demands for animal feed (also a food security subject), as well as its importance for ecosystem maintenance and biodiversity conservation concerns (e.g. sustenance of food chain for primary consumers and decomposers, soil stabilization and erosion prevention etc.). The energetic use of UnE is therefore expected to be trade-off between energy provision and food security or between energy provision and ecosystem maintenance. The method adopted involved the estimation of the different component of the HANPP using data outputs from the GAEZ model (1960-2000 for baseline setting) and the EPIC model (2000 to 2030, 2050, and 2070 respectively for the spatio-temporal assessment); as well as conversion factors from recent global HANPP assessments published in literature. This is followed by a three-prong (energy, greenhouse gas, and water footprint) spatio-temporal LCA of the three relevant HANPP components (namely the HG, ER, and UnE) for evaluation of the energy provision, GHG regulation, and fresh water conservation potentials within global agro-bioenergy system context.
Final results of applying the coupled HANPP-LCA methodology suggests that the most efficient way of maximizing biomass for agro-bioenergy production with reduced environmental impacts (in terms of water usage and greenhouse gas emissions), higher energy gains and efficiencies (enough to meet World Energy Council’s projected energy demands from biomass) and advantages for transitions to bio-economy, without conflicting with food security, ecosystem maintenance, and biodiversity conservation concerns is through the energetic reuse or cascade use of extracted residues, even though the strategies for achieving this is not yet clear.
Juraj Balkovic and Ligia Azevedo, Ecosystem Services and Management Program, IIASA
Oludunsin Tunrayo Arodudu, of the Leibniz Centre for Agricultural Landscape Research and University of Potsdam, Germany, is a citizen of Nigeria. He was funded by the IIASA German National Member Organization and worked in the Ecosystem Services and Management Program during the YSSP.
Please note these Proceedings have received limited or no review from supervisors and IIASA program directors, and the views and results expressed therein do not necessarily represent IIASA, its National Member Organizations, or other organizations supporting the work.
Last edited: 02 February 2016
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