Abstract
Microbial electrosynthesis (MES) allows carbon-waste and renewable electricity valorization into industrially-relevant chemicals. MES has received much attention in laboratory-scale research, although a techno-economic-driven roadmap towards validation and large-scale demonstration of the technology is lacking. In this work, two main integrated systems were modelled, centered on (1) MES-from-CO2 and (2) MES from short-chain carboxylates, both for the production of pure, or mixture of, acetate, n–butyrate, and n–caproate. Twenty eight key parameters were identified, and their impact on techno-economic feasibility of the systems assessed. The main capital and operating costs were found to be the anode material cost (59%) and the electricity consumption (up to 69%), respectively. Under current state-of-the-art MES performance and economic conditions, these systems were found non-viable. However, it was demonstrated that sole improvement of MES performance, independent of improvement of non-technological parameters, would result in profitability. In otherwise state-of-the-art conditions, an improved electron selectivity (≥36%) towards n-caproate, especially at the expense of acetate, was showed to result in positive net present values (i.e. profitability; NPV). Cell voltage, faradaic efficiency, and current density also have significant impact on both the capital and operating costs. Variation in electricity cost on overall process feasibility was also investigated, with a cost lower than 0.045 € kWh−1 resulting in positive NPV of the state-of-the-art scenario. Maximum purification costs were also determined to assess the integration of a product’s separation unit, which was showed possible at positive NPV. Finally, we briefly discuss CO2 electroreduction versus MES, and their potential market complementarities.
Highlights
The concept of circular economy is a solution to series of challenges such as waste generation, resource scarcity, and sustaining economic benefits
As defined by Bonk et al (2015), we introduced a maximum purification cost (MPC) that represents the maximum cost of separation to reach a net present value of zero for the overall process [12]
We developed a techno-economic model consisting of integrated engineering and economic modules for the detailed assessment of microbial electrosynthesis systems
Summary
The concept of circular economy is a solution to series of challenges such as waste generation, resource scarcity, and sustaining economic benefits. Organic wastes into chemicals, fuels, feed, and food without any harmful emission into the environment could have the potential to contribute to the envisioned circular biobased economy [2]. Microbial electrosynthesis (MES) is an electrified biotechnology, i.e. an electricity-driven production platform, that allows converting electrical power and carbon building blocks into valuable chemicals such as medium chain carboxylic acids (MCCAs), as schematized in Fig. 1 [3]. MES relies on electroactive microorganisms, i.e. biocatalysts which utilize electrons from a solid-state electrode as their main energy source, for the conversion of CO2 and/or organics. MES could allow to store and increase the value of electrical energy produced from intermittent renewable sources such as solar and wind [4]. MES uses minimal amounts of water (ca. 1–5 kgH2O kg− 1product), when calculated from current density and considering water oxidation at the anode electrode
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