Using Techno-Economic Modelling to Determine the Minimum Cost Possible for a Microbial Palm Oil Substitute

Abstract

Background Palm oil is the most commonly used crop oil worldwide, and is used predominantly for food, in the chemical industry and for biofuels. It is mainly cultivated in areas with biodiverse and carbon-rich rainforest which has given rise to large increases in greenhouse gas (GHG) emissions and significant impacts to biodiversity. There is therefore substantial interest in finding an alternative to palm oil. Heterotrophic single cell oils (SCOs) are one potential replacement as these are able to mimic the lipid profile of palm oil in a way that other terrestrial and exotic crop oils cannot. But, despite a large experimental research effort in this area, there are only a handful of techno-economic modelling publications. As such, there is little understanding of whether SCOs are, or could ever be, a potential competitive replacement to palm oil. To help address this question we designed a detailed model that coupled a hypothetical heterotroph (using the very best possible biological lipid production) with the largest and most efficient chemical plant design possible. Results Our base case gave a lipid selling price of $2.01 / kg for ~8,000 tonnes / year production, that could be reduced to $1.54 /kg on increasing production to ~48,000 tonnes of lipid a year. A range of scenarios to further reduce this cost were then assessed, including using a thermotolerant strain (reducing the cost from $1.54 /kg to $1.47 /kg), zero cost electricity ($ 1.48/kg), using non-sterile conditions ($1.05 / kg), wet extraction of lipids ($1.48 / kg), continuous production of extracellular lipid ($0.76 /kg) and selling the whole yeast cell, including recovering value for the protein and carbohydrate ($1.14 /kg). If co-products were produced alongside the lipid then the price could be effectively reduced to $0, depending on the amount of carbon funnelled away from lipid production, as long as the co-product could be sold in excess of $1/kg. Conclusions The model presented here represents an ideal case that which while not achievable in reality, importantly would not be able to be improved on, irrespective of the scientific advances in this area. From the scenarios explored, however, it should still be possible to produce lower cost SCOs, but research must start to be applied in three key areas, firstly designing products where the whole cell is used, displacing products that contain palm oil rather than attempting to produce an exact refined palm oil substitute. Secondly, further work on the product systems that produce lipids extracellularly in a continuous processing methodology or finally that create an effective biorefinery designed to produce a low molecular weight, bulk chemical, alongside the lipid. All other research areas will only ever give incremental gains rather than leading towards an economically competitive, sustainable, microbial oil.

Production of human milk fat substitute by engineered strains of Yarrowia lipolytica

“…The highest productivity in terms of lipids has been reported for GE strains in nitrogen-limited glucose-fed batch culture, where 1.2 g -1 L -1 h -1 has been achieved (Qiao et al, 2017). It is noteworthy that similar or higher lipid productivities have also been reported for Rhodosporidium toruloides, Rhodotorula glutinis and Lipomyces starkeyi yeasts cultivated on glucose (Karamerou et al, 2021). The Y. lipolytica strain used in this study has not been engineered to improve its total FA composition, but modification of this trait is possible based on the findings of previous studies (Ledesma-Amaro and Nicaud, 2016;Tsakraklides et al, 2018).…”

“…Ultimately, a thorough technoeconomic analysis is required to determine what the lowest cost microbial fermentation process would likely be for HMFS production. However, for heterotrophic growth of oleaginous yeast on sugar substrates, many analyses have already been made that may be applicable, owing to interest in microbial production of similar lipids such as palm oil substitute (Karamerou et al, 2021). Karamerou et al, (2021) recently estimated that the lowest selling cost it may be theoretically possible to reach is ~$1.2 kg -1 for a production scale of 48k tonnes yr -1 .…”

“…However, for heterotrophic growth of oleaginous yeast on sugar substrates, many analyses have already been made that may be applicable, owing to interest in microbial production of similar lipids such as palm oil substitute (Karamerou et al, 2021). Karamerou et al, (2021) recently estimated that the lowest selling cost it may be theoretically possible to reach is ~$1.2 kg -1 for a production scale of 48k tonnes yr -1 . Market research suggests that HMFS production is on a similar scale and the price exceeds ~$6 kg -1 .…”