Valorisation of source-separated food waste to bioethanol: pilot-scale demonstration

Abstract

Food waste is a waste stream that is produced globally in huge amounts and therefore constitutes a major environmental concern. Additionally, the growing consumption of fossil fuels sets the need for alternative energy sources. To this end, in this paper, an holistic approach towards bioethanol production from source-separated food waste was studied as an effective strategy to cope with both issues. Source-separated food waste collected from a Greek Municipality was used as raw material. Two fermentation modes, separate hydrolysis and fermentation and simultaneous saccharification and fermentation, were examined in laboratory and pilot scales with varying solids loadings. For separate hydrolysis and fermentation (SHF) trials, the solids loading increase led to a significant ethanol yield reduction from 79 to 55 g/kg food waste, whereas for simultaneous saccharification and fermentation (SSF), the ethanol yield was increased by 77% (from 62 to 110 g/kg food waste) as the solids loading was increased. This is also related to greater ethanol concentrations, which are beneficial in terms of technoeconomics. The lowest bioethanol production cost, 1.57 €/kg ethanol, was estimated for the scenario of SSF with 20% solids loading while for SHF the lowest production cost was achieved (4.40 €/kg ethanol) when 15% solids loading is applied. In most cases, the energy and enzyme costs presented the most pronounced impact on the total bioethanol cost. In conclusion, it was proved that the food waste valorisation towards bioethanol production is technically feasible on a pilot scale. However, further techno-economic factors of the whole value chain must also be taken into consideration while aiming to assess the viability of the process.

Sustainable Bioethanol Production by Solid State Fermentation: A Systematic Review

“…These media modi cations have also altered T. reesei morphology with denser and highly branched mycelia, causing larger surface area for enzyme-substrate interaction and resulting an elevated enzyme production (Zapata et al, 2018). The increase of solid loading during SSF leads to an increase of ethanol production as reported by Passadis et al Higher solids loadings imply higher carbohydrates loading, higher glucose production and higher ethanol production (Passadis et al, 2022)…”

“…Different studies compared the production of bioethanol and enzymes by SSF and SmF. Higher yields of SSF compared with SmF were observed in the study of Passadis et al where the ethanol yields were higher (up to 30%) during SSF (Passadis et al, 2022).…”

“…fumigatus was recorded at the temperature of 30°C, a drop or rise of temperature of 30°C will cause a decline in cellulase production (Fadela et al, 2021). Passadis et al evaluated different temperature for optimum enzymatic sacchari cation of starch and cellulose and the temperature of 35°C is favorable, given that higher energy is required to maintain higher temperature (Passadis et al, 2022).…”

Food Waste to Bioethanol: Opportunities and Challenges

“…The majority of the bioethanol production bioprocesses developed with FLW are submerged fermentations. The common configuration for the bioreactors used in the submerged fermentation is rushton impellers, baffles, aerated vessels, and continuous stirring for batch processes [106,135,159,168,174]. The economic bioethanol production using FLW will require high solid loading.…”

Process simulation–based scenario analysis of scaled-up bioethanol production from water hyacinth

“…Since the single reactor accommodates the saccharified products to be consumed by microorganisms instantly, the formation of inhibitors is prevented, unlike in SHF [ 41 ]. Hence, a new scaled-up process would include SSF instead of conventional SHF [ 42 ]. For application as fuel-grade bioethanol, the end product requires a minimum purity of 99.5 vol% [ 10 ].…”