Just the tonic! Legume biorefining for alcohol has the potential to reduce Europe's protein deficit and mitigate climate change

Theophile Lienhardt,Kirsty Black,Sophie Saget,Marcela Porto Costa,David Chadwick,Robert M Rees,Michael Williams,Charles Spillane,Pietro M Iannetta,Graeme Walker,David Styles

doi:10.1016/j.envint.2019.05.064

Abstract

Industrialised agriculture is heavily reliant upon synthetic nitrogen fertilisers and imported protein feeds, posing environmental and food security challenges. Increasing the cultivation of leguminous crops that biologically fix nitrogen and provide high protein feed and food could help to address these challenges. We report on the innovative use of an important leguminous crop, pea (Pisum sativum L.), as a source of starch for alcohol (gin) production, yielding protein-rich animal feed as a co-product. We undertook life cycle assessment (LCA) to compare the environmental footprint of 1 L of packaged gin produced from either 1.43 kg of wheat grain or 2.42 kg of peas via fermentation and distillation into neutral spirit. Allocated environmental footprints for pea-gin were smaller than for wheat-gin across 12 of 14 environmental impact categories considered. Global warming, resource depletion, human toxicity, acidification and terrestrial eutrophication footprints were, respectively, 12%, 15%, 15%, 48% and 68% smaller, but direct land occupation was 112% greater, for pea-gin versus wheat-gin. Expansion of LCA boundaries indicated that co-products arising from the production of 1 L of wheat- or pea-gin could substitute up to 0.33 or 0.66 kg soybean animal feed, respectively, mitigating considerable greenhouse gas emissions associated with land clearing, cultivation, processing and transport of such feed. For pea-gin, this mitigation effect exceeds emissions from gin production and packaging, so that each L of bottled pea gin avoids 2.2 kg CO2 eq. There is great potential to scale the use of legume starches in production of alcoholic beverages and biofuels, reducing dependence on Latin American soybean associated with deforestation and offering considerable global mitigation potential in terms of climate change and nutrient leakage — estimated at circa 439 Tg CO2 eq. and 8.45 Tg N eq. annually.

Highlights

Industrialised agriculture systems are heavily dependent on the application of synthetic nitrogen (N) fertiliser, around half of which is not assimilated by the target crop but lost to the environment
Expanded boundaries encompassed: (i) cultivation of wheat or pea crops; (ii) de-hulling of peas and milling of pea kernels and wheat grain into grist; (iii) distillery operations; (iv) gin bottling and packaging for distribution; (v) management of pot-ale as either land-spread fertiliser or animal feed, processed into dried distillers' grains with solubles (DDGS) for the latter use; (vi) credits for avoided production, transport of synthetic N fertilisers and avoided animal feed; and (vii) avoided land use change from spared soybean meal, and incurred land use change from net additional UK cropland requirements
Allocation of system burdens across gin and animal feed co-products indicated that gin produced from peas had a smaller environmental footprint than gin produced from wheat across 12 of 14 environmental impact categories considered, including 12%, 48% and 68% smaller global warming, acidification and eutrophication burdens, respectively

Summary

Introduction

Industrialised agriculture systems are heavily dependent on the application of synthetic nitrogen (N) fertiliser, around half of which is not assimilated by the target crop but lost to the environment. Life cycle assessment (LCA) studies have demonstrated that legumes can reduce GHG emissions in arable rotations compared with cereals and other crops that depend on synthetic N fertiliser (Nemecek et al, 2008, 2015). Grain legume cultivation, primarily peas (Pisum sativum L.) and faba bean (Vicia faba L.), occupies just 1.5% of arable land in the European Union (EU) (Watson et al, 2017); insufficient to support significant BNF or ecosystem services delivery at landscape scale (Iannetta et al, 2016). There is growing concern about Europe's dependence on imports to meet 70% of protein-feed fed to pigs, poultry, cattle and fish (Thomassen et al, 2008; de Visser et al, 2014; De Santis et al, 2016; Watson et al, 2017; European Commission, 2018b), in particular milled grains of the legume soybean (Glycine max L). There is strong interest in substitution of soy-based feeds to improve the sustainability and resilience of European livestock and expanding aquaculture systems (Hortenhuber et al, 2011; Schader et al, 2015; De Santis et al, 2016)

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Conclusion