Emergy synthesis of a combined food and energy production system compared to a conventional wheat (Triticum aestivum) production system

Abstract

It is a major challenge to produce food and energy sustainably for the ever increasing world population as today's conventional food production and energy needs are met by the fossil based resources, causing enormous environmental load. A novel, combined food and energy (CFE) agro-ecosystem, was designed for sustainable production of food, fodder and energy without chemical inputs (fertiliser, herbicide and fungicide). The objective was an emergy synthesis of the CFE system compared to a conventional wheat (Triticum aestivum) production system to assess resource use efficiency. The emergy indices, used to assess the environmental performance and sustainability, exhibited contrasting differences between the two production systems in terms of outputs (Y), total emergy use, solar transformity, relative use of local renewable resources, environmental loading ratio (ELR), emergy yield ratio (EYR) and emergy sustainability index (ESI). The Y in the CFE consisted of grain, straw, fodder and woodchip production of 4020, 3580, 6100 and 10,000kg/ha/yr respectively whereas Y in the conventional wheat consisted of 7250 and 3770kg grain and straw/ha/yr respectively. The Y in the CFE was 81% (2.80E+11J/ha/yr) higher with 13.5 times (6.40E+03seJ/J) lower solar transformity compared to the Y (1.54E+11J/ha/yr) and solar transformity (8.63E+04seJ/J) in the conventional wheat, exhibiting highly resource intensive production in conventional wheat. The local renewables constituted 19.2% and 2.6% of the total emergy input in the CFE and the conventional wheat respectively with a corresponding lower ELR (4.21) and 22.5% higher EYR (1.26) in CFE compared to conventional wheat. CFE was more reliant on local renewable emergy flows and compatible with the local environment with higher ESI (0.30) compared to conventional wheat (0.03), where 64.5% of the total emergy input constituted chemical inputs. The study demonstrated that the innovative agro-ecosystem, exemplified by CFE, is considerably less resource demanding and more amenable to sustainable production, whether defined in terms of outputs, solar transformity, relative use of local renewable resources, EYR, ELR or ESI.