Planet Health
Carbon Negative Production of Commodity Chemicals
Introduction. The modern chemical industry does an amazing job of converting fossilized vegetative matter into products essential for modern lifestyles. Currently, the industry releases significant quantities of CO2 into the atmosphere. We propose to establish innovative technology to reverse this detrimental consequence. The new biotechnology will both directly and indirectly pull CO2 from the atmosphere to convert it into new materials for producing durable goods. Overall, this can contribute significantly toward sustainable mitigation of global warming.
The transformational advance is efficient transfer of electrons from renewable electricity into biomolecular synthesis using cell-free bioprocessing. However, economically attractive bioprocess technology requires the coordinated development of several synergistic advances. CO2 will be drawn from the exhaust gases of bioethanol facilities. Initially, glucose will also be used as a raw material since it is available from the corn starch produced locally and contains carbon fixed from the atmosphere by the corn plants. This foundational technology, designed to produce succinic acid, will then allow the transition to technologies using CO2 as the only carbon source. We envision a new chemical industry that will contribute significantly toward stopping global warming while also providing thousands of good jobs in the corn belt.
Process Concepts. The overall process is diagramed in Figure 1. The heart of the system is a cell-free reactor with catalysis provided by a crude cell extract. The extract will be produced from an engineered E.coli culture with overexpressed pathway proteins. During preparation, the extract will be triggered to inactivate enzymes catalyzing side reactions that would otherwise lower conversion yields.
Figure 1. Conceptual diagram for carbon negative, cell-free succinic acid production.
The lysate will harvest electrons from H2 provided by an electrolyzer and transfer them as needed. These extra electrons will allow two CO2 molecules and one glucose molecule to be converted into two molecules of succinate. This provides much higher glucose conversion yields and fixes CO2 from bioethanol offgas into a biochemical that can potentially find its way into a plastic or other useful product.
The cell-free approach allows on-line monitoring of reaction intermediates so that glucose and CO2 feeding and other adjustments can be made to support very high and sustained volumetric productivities. This performance will require continuous product removal, indicated in Figure 1 by the ultrafiltration (UF) unit that will retain enzymes in the reactor while removing the aqueous continuous phase containing accumulated succinate, enzyme co-factors, and reaction intermediates. The succinate can readily and specifically be removed by an anion exchange capture column. The recycle fluid will then be returned to the reactor after flowing through a chamber (pink color) designed to kill possible microbial contamination and to condition the fluid to maintain catalytic reactivity.
A preliminary technoeconomic analysis suggests that this process can provide excellent profitability as well as an attractive return on investment.