The capture of carbon dioxide before or after it is emitted has been regarded as a crucial mitigation pathway to prevent the rapidly increasing accumulation of CO2 in the atmosphere. The valorisation of the captured CO2 into value added products such as methanol provides an additional economic incentive to continue developing these technologies. The company Zero Emission Fuels B.V. (ZEF) is currently developing a mass-producible miniature methanol plant that houses a Direct Air Capture and CO2-compression unit, an Alkaline Electrolysis Cell, a Methanol Reactor, and a Distillation unit. Potential benefits of this approach are in the economies of scale of production, and autonomous operation in areas of high solar irradiation due to direct integration with PV systems.
To validate the microplant-concept from an environmental perspective, a research project was executed with the goal to establish the environmental profile of the microplant, to identify hotspots for impact mitigation, and to assess the position of the microplant’s environmental profile in relation to results of comparable technologies reported in literature. To do so, multiple technological development pathways were considered that project the current microplant’s performance into a range of future states.

The impact assessment of the future PV-powered air-to-methanol plant, suggests that it is likely that methanol produced using this approach will exhibit a low (negative cradle-to-gate) climate change impact along its production chain, especially compared to conventional methanol produced via the steam reforming of natural gas. Environmental trade-offs are incurred by the additional material demand compared to conventional methanol, instilled both by the electricity generation from PV panels and the added material demand of the thousands of micro-plants that need to be produced for sufficient methanol production volume.
Using polyamine sorbents for the process of capturing CO2 from the atmosphere inevitably leads to sorbent degradation which in turn can cause emissions of various substances. Using rough estimations via a worst/best case approach, it was analysed that emissions from the capture unit are relevant in three impact categories.
Overall, the additional material demand and sorbent-related emissions introduce significant trade-offs in between 5-8 impact categories, depending on the followed technological scenarios. Additional technological improvement may reduce the trade-off effect, leading to a reduction of trade-off categories to a number of four.

The analysis concluded that it is likely that there are benefits to using the microplant-approach to methanol production, though additional research is critical to iron out the large uncertainties that are paired with future-oriented life cycle assessment.