Abstract
AbstractThe meat and dairy industry across Europe is dependent on the production of grass. However, faced with competing pressures to reduce the environmental impact of agriculture, a potential future reduction of meat and dairy consumption in western diets, and pressure to minimize food production costs, grass could be used to produce alternative products. The biological production of polyhydroxyalkanoates (PHA) by using grass as the primary carbon source in a novel mixed culture process has been studied. A total of 30,000 t of fresh grass would yield approximately 403.65 t of dried biopolymer granules. On the basis of this early stage, non‐optimized process, the cumulative energy demand (CED) of PHA produced from waste grass and cultivated grass was found to be 248.4 MJ/kg and 271.8 MJ/kg, respectively, which is the same order of magnitude as fossil‐carbon‐based polymers. Improvements in volatile fatty acid yields, reduction in chemical and water inputs, and using residues to make other products will reduce the CED. Given the future requirement to produce polymers with little or no fossil‐carbon feedstock, an optimized version of the process could provide a viable future production option that also contributes to the long‐term sustainability of agricultural communities.
Highlights
The growing of forage and fodder grasses is of critical importance to European Union (EU) agriculture because they provide the main feeds supporting the production of dairy and beef cows
This study aims to evaluate the potential of utilizing grass to produce high value products, polyhydroxyalkanoate (PHA) biopolymers, in a biorefinery approach
As urban grass waste is currently collected by municipal authorities in many parts of Europe regardless of the treatment route, the production and collection of this feedstock has not been included in the evaluation
Summary
The growing of forage and fodder grasses is of critical importance to European Union (EU) agriculture because they provide the main feeds supporting the production of dairy and beef cows. Whilst grass is a mainstay of global agriculture there are a number of pressures acting at regional and national scales that suggest a possible future scenario where grass is grown for other purposes than for rearing animals. The large resource and environmental burdens of rearing animals, primarily as a source of protein for human consumption, coupled with the human health impacts of over consumption of meat in many diets leads to the potential scenario of reducing intensive meat production in some regions (Chai et al, 2019). In the UK green waste is predominantly treated via composting with the resulting compost sold for horticultural/agricultural use. Production of compost from green waste is net energy negative (Martínez-Blanco et al, 2010), generates greenhouse gas (GHG) emissions (Vergara & Silver, 2019), and, whilst providing the service of returning carbon and nutrients to land, is generally considered as a low value product
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