Renewable CO₂recycling and synthetic fuel production in a marine environment

Abstract

A massive reduction in CO 2 emissions from fossil fuel burning is required to limit the extent of global warming. However, carbonbased liquid fuels will in the foreseeable future continue to be important energy storage media. We propose a combination of largely existing technologies to use solar energy to recycle atmospheric CO 2 into a liquid fuel. Our concept is clusters of marinebased floating islands, on which photovoltaic cells convert sunlight into electrical energy to produce H 2 and to extract CO 2 from seawater, where it is in equilibrium with the atmosphere. These gases are then reacted to form the energy carrier methanol, which is conveniently shipped to the end consumer. The present work initiates the development of this concept and highlights relevant questions in physics, chemistry, and mechanics. renewable energy | carbon dioxide recycling | synthetic fuel | maritime structures L imiting anthropogenic global warming to below 2°C, a goal of the Paris Agreement of the United Nations Framework Convention on Climate Change (1), now ratified by 174 countries, will require within the coming decades the phasing out of carbon dioxide emissions from fossil fuel burning. However, in the foreseeable future, carbon-based liquid fuels will continue to play an important role, in particular for aeronautical, marine, and long-haul automotive mobility. It is therefore essential to investigate possibilities of using renewable energy to recycle CO 2 between the atmosphere and synthetic liquid fuel (2). Efforts to photochemically produce synthetic fuel from CO 2 and water (i.e., via artificial photosynthesis) show some promise (3). We propose an approach using more conventional methods, but with important unique aspects.Methanol, CH 3 OH or MeOH, is the simplest carbon-based fuel, which is liquid at ambient conditions (4). With approximately half the energy density of gasoline (15.6 MJ/L vs. 32.4 MJ/L), it can be used to power existing gas turbines, modified diesel engines, and direct methanol fuel cells. Methanol can serve as a feedstock for most petrochemical products, and by simple dehydration it can be converted to dimethyl ether, an attractive substitute for natural gas, and other hydrocarbon fuels. Methanol can be produced (5) by the catalytic hydrogenation of CO 2 [presently the largest methanol production facility using this technique is located in Iceland (6)], and MeOH burns in air to release CO 2 and water:An attractive scenario for the production of synthetic methanol fuel is the recycling of atmospheric CO 2 , the electrolytic produc-tion of H 2 , and their catalytic reaction to CH 3 OH, with all of these processes powered by renewable energy. As a concept for realizing this scenario, the present work proposes the production of H 2 and the extraction of CO 2 from seawater and their catalytic reaction to produce MeOH on clusters of artificial, marine-based photovoltaic (PV)-powered "solar methanol islands" (7) (Fig. 1). We present an initial implementation plan; in view of many uncertainties, much addition...

A direct coupled electrochemical system for capture and conversion of CO2 from oceanwater

“…World ocean constitutes the largest carbon sink, absorbing about 40% of anthropogenic CO 2 since the beginning of industrial era 24 – 26 with an effective CO 2 concentration of 2.1 mmol kg −1 , or 0.095 kg m −3 in oceanwater, which is a factor of 120 times larger than in the atmosphere 27 – 29 . Thus, CO 2 capture from oceanwater provides an alternative and unique approach to direct air capture (DAC) in the global carbon removal technological landscape 30 . CO 2 capture from oceanwater, however, presents many challenges.…”

Carbon Capture From Flue Gas and the Atmosphere: A Perspective

“…Patterson et al proposed an approach to recycle atmospheric CO 2 into liquid fuels on a large-scale marine-based artificial island, using renewable energy (solar or wind) to power the production of hydrogen and CO 2 extraction from seawater, followed by catalytic conversion to liquid methanol fuel (Patterson et al, 2019). The major advantage of the proposed FIGURE 8 | Concept of one step direct integration of CO 2 capture and in situ CO 2 conversion.…”

Endangered elements, critical raw materials and conflict minerals

“…91 As coupled with a state-of-the-art, low-cost, PV mini-module, based on a perovskite, a 2.3% solar-to-hydrocarbon efficiency was achieved, which is considered to set a benchmark for an inexpensive, all-Earth-abundant PV–EC system. 91 It has been proposed 92 to instal floating ‘solar methanol islands’ with the facility to produce H 2 from the PV electrolysis of seawater, from which CO 2 is also extracted. The reaction between these materials using a selective catalyst (e.g.…”

“…In order to make enough methanol to substitute for all the fossil-derived fuels that are used globally by long-haul transportation, it was reckoned that probably 170,000 such islands would be needed, and which would have to be located in ocean regions where the waves are less than 2 m high, and where sufficient sunlight is received, annually, to meet the energy requirements of the process. 92…”