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MPhil in Engineering for Sustainable Development

global challenges, engineering solutions

Studying at Cambridge

Katherine Bruce


Every year an estimated 6.5 million tonnes of fossil-based plastics are used in the
agricultural sector, of which the largest fraction is plastic mulch films. These films are
inherently challenging to recycle, and farmers typically dispose of the films in a
landfill. Research to date has focused on the use of biodegradable bio-plastics as an
alternative to fossil-based film. Widespread production of bio-plastics may
compromise food security as the growth of bio-crops competes with existing
agricultural land. Agricultural waste, such as straw, a by-product of cereals
cultivation, presents a viable, inexpensive carbon feedstock. Scaling up the resource
as a feedstock for bio-plastic mulch film is an unexplored area of research.

Here, a framework is presented to assess the feasibility of sourcing agricultural waste
as a feedstock for bioplastic mulch film in the UK. The framework is based on four
sequential steps, starting from a holistic, nationwide perspective to value generation
on an individual scale. Each step was analysed via primary or secondary data and
linked to one of the three sustainability pillars (economic, social and environmental).

Findings show that the UK produces 3.7 million tonnes of currently untapped crop
residue every year. The resource could be exploited to produce 0.52 million
tonnes/year of bioplastic mulch film – 8 times higher than the current demand of
mulch film. Cereals farmers would generate valuable additional revenue from the
resource (up to £22k annually). However, horticultural farmers would pay £100/ha
more on average to use bio-plastic mulch film than plastic mulch film. Furthermore,
farmers expressed concerns about the long-term impact of bio-plastic mulch film on
their soil. A review of available lifecycle assessments indicated no significant

differences between bio-plastic and plastic mulch film. Nevertheless, using straw as a
resource reduces land-use emissions associated with virgin bio-plastic feedstock.
Bridging the gap between cereal farmers and bio-refineries, increasing agricultural
landfills tax to encourage a transition to bio-plastic films and further studies on the
environmental impacts are some of the proposed steps to overcome current barriers.
The strategic framework serves as a precedent for similar assessments in other
countries to critically evaluate utilisation of straw as a feedstock.