Carbon dioxide emissions into the atmosphere continue to grow at an alarming rate. In 2010, some 33 billion tons of CO2 were emitted, while 12.5 billion tons from power generation plants, 9.5 billion tons from various industrial processes and 5 billion tons from road transport were poured in the atmosphere. While the rate of growth of CO2 emissions has fallen somewhat in the industrialized nations, the emissions from the developing economies, notably China and India are galloping. There are no immediate alternatives to fossil fuel based power generation and road transport. Many expensive solutions for carbon capture and sequestration are being tried, including storage in underground caverns and in deep sea water. Some environmentalists are worried about the long term safety of such storage and believe leaks or accidents would cause the sequestered CO2 to leak, nullifying all this effort. There is a need to find alternative technologies that can capture and convert CO2 into a more benign gas.
Need for change
One stream of research is to try, in effect, to recycle CO2 back into usable fuel. If the CO2 could be split into Carbon Monoxide and Oxygen, the CO can be converted into hydrocarbons by adding hydrogen molecules through the well established Fisher-Tropsch process. The catch is that this process is energy-intensive. If that energy comes from fossil fuels, the purpose is defeated. The attempt, therefore, is to use solar energy to accomplish this splitting. These include both industrial conversion processes and the use of bio-catalysts to speed up the slow natural photosynthesis process.
1. Sunshine to Petrol project
The US Government’s Sandia National Labs of Albuquerque, New Mexico is building this solar reactor to convert CO2 emissions from a power plant into fuel. They have named this the Sunshine to Petrol project. The reactor is called the CR5 (for Converter Rotating Ring Receiver Reactor Recuperator). It uses large parabolic mirrors to direct sunlight onto 14 rotating rings made of cobalt-ferrite, heating them to a temperature of 2600 degrees F. At this temperature, the ferrite releases oxygen. The rotating ring then turns into a chamber pumped with CO2 gas from the power plant emissions. The ferrite absorbs one molecule of oxygen from the CO2 and converts it into Carbon Monoxide. In another chamber water is sprayed, which turns into steam on contact with the heated ferrite ring. The ferrite absorbs oxygen molecules from the water vapor and releases hydrogen. The hydrogen and carbon monoxide generated in the two chambers are combined to produces synthetic hydrocarbons. The ferrite rings rotate back into the sunlight, release oxygen and the cycle continues.
The technology is still many years away from commercial deployment but the scientists at the Sandia labs suggest that, if successful, fossil fuel power plants could be retro-fitted with banks of such reactors to capture CO2 at the point of emission and produce synthetic hydrocarbons.
2. Bacteria to convert CO2 into liquid fuel
While the Sandia Labs project is an industrial process for converting CO2 into fuel, this project by researchers from UCLA’s Henry Samueli School of Engineering and Applied Sciences uses genetic engineering.The researchers have genetically modified a cyanobacterium to consume CO2 in the presence of sunlight and convert it into iso-butanol, a hydrocarbon.The scientists postulate that these bacteria be cultivated in the open spaces around a fossil power plant.
In a similar appraoch, a Cambridge, Massachusetts start-up Joule Biotechnologies has received a patent for genetically modified cyanobacteria for production of ethanol from CO2. This company already has a pilot project operating in Texas and claims that this technology can produce 25,000 gallons of ethanol per acre and will use only sunlight and non-potable water as inputs. This high yield per acre will help address the criticism against growing bio-fuel crops on land previously used for food crops which led to rise prices of corn and other food grains. The bio-fuel crops also need additional processing to convert bio-mass into fuel.
Another technology company, Carbon Sciences of Santa Barbara, California is pursuing the development of bio-catalytic reactors that will convert CO2 and Water into fuels like ethanol. This company has already demonstrated some success in converting CO2 into Calcium Carbonate that is used in the paper and the paints industries.
There are many many companies working on variants of using bacteria for carbon capture.
These early success stories have opened our thinking to the idea that CO2 may one day be recycled into fuel. This will attract more researchers and money into this field. Hitherto, all the effort was to contain CO2 emissions or to sequester it for future generations, using expensive methods.
What difference will it make
While these technologies are still at the laboratory concept stage, the hope is that if any of these goes on to become a viable technology for carbon capture and recycling, the threat of global warming would abate. That would permit the world to continue to use fossil fuels like coal to meet the energy demand for the developing nations that find renewable energy still too expensive.
As with any new technology, the concern is with the cost of the technology and the unknowns in terms of any negative effects. In the first flush of all new scientific discovery, the euphoria factor predominates. Once these ideas are tried out in pilot plants and scaled up, new problems emerge that would need further work. We need to watch for these steps before reaching a conclusion on the viability of these technologies.