Abstract
Food processing can generate large amounts of carbohydrate-rich waste that inevitably has environmental and social impacts. Meanwhile, certain heterotrophic marine microorganisms, including algae and thraustochytrids, have the potential to convert carbohydrate-rich substrates into oil-rich biomass over relatively short time frames. To assess the merits of this apparent synergy, an initial conceptual process was developed based on the use of raw potato processing waste as feed in an algal bioreactor to produce bio-oil for further use within the food industry. A practical flowsheet was established with a conventional 200 kL bioreactor whereby the unit processes were identified, the mass balance developed, and estimates made of the various material and energy demands. These inputs were used to develop a baseline life cycle assessment (LCA) model and to identify opportunities for reducing environmental impacts. With the functional unit (FU) being 1 tonne cooking oil, the baseline configuration had a greenhouse gas (GHG) footprint of 2.4 t CO2-e/FU, which is comparable to conventional process routes. More detailed LCA revealed that electricity for stirring the bioreactor contributed approximately 78% of the total GHG footprint. By adjusting the operating conditions, the most promising scenario produced 0.85 t CO2-e/FU—approximately four times less than the conventional process—and shows the potential advantages of applying LCA as a tool to develop and design a new production process.
Highlights
Waste residue generated from food manufacturing is significant both in Australia and internationally [1,2,3]
The present study demonstrates how life cycle assessment (LCA) can be utilized to guide new process design in the case of potato processing waste and its subsequent conversion to useful products
From an initial calculation of base case energy consumption per batch of biomass product from a 200 kL reactor (Table A3), the base case greenhouse gas (GHG) footprint was calculated as 2.4 t CO2 -e/functional unit (FU) (Figure 2)
Summary
Waste residue generated from food manufacturing is significant both in Australia and internationally [1,2,3]. For a leading Australian food manufacturer that processes over 300,000 tonnes of fresh potatoes each year [4], around 50% of the intake material can be viewed as waste due to loss in the fresh potato supply chain, including field loss (1–2%), grading loss (3–13%), storage loss (3–5%), packing loss (20–25%), and retail waste (1.5–3%) [5,6]. Processing this waste economically and with minimal environmental impact is a significant challenge for industry and the community. Use of low value biomass residuals and/or waste streams as a feedstock avoids the controversy surrounding the use of food crops for fuel, while potentially mitigating other social and environmental concerns
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