Bursting the Carbon Capture, Utilisation and Storage myth
The problem with bandwagons is that people who join them don’t really understand them. A growing number of people think we can make something useful out of waste carbon dioxide without any problem. Make sustainable fuels! Great idea…..problem solved…..hey presto!
Energy balances
The real problem is the energy balance. Carbon dioxide is what you get when a carbonaceous fuel is burnt to yield its energy. Fossil fuels are high in energy because they were formed years ago from organic matter ultimately energised by the sun. They combine with oxygen and give up their energy for us to use. The carbon dioxide is formed because it represents a lower energy state, and the universe is constantly seeking the stability of the lower energy state; something the universe is constantly seeking. That’s why silicon is such a common material in nature. It’s the atom you ended up with after higher energy atoms disintegrated in the big bang.
A use for carbon dioxide?
So, to make a carbonaceous fuel such as SAF by using carbon dioxide as a raw material, you must put all that energy and more back into it. Almost every day some new announcement is made that scientists have a new process for extracting CO2 from the air and turning into fuel. But they don’t dwell on the energy they have to input and where it’s to come from. New catalyst formulations are frequently developed but they don’t affect the energy deficit at the heart of the dilemma, only the speed and selectivity of the reaction towards the equilibrium.
Adding green hydrogen
Green hydrogen (produced by electrolysis of water using renewable electricity) can be the source of the energy, but its production requires a great deal of power. Other electrolytic systems have been tried but again the power needed is high. Converting carbon dioxide into fuels is therefore not as simple as it sounds, and we must always be wary of where the energy is coming from.
Bio-crops have to compete
Some processes under development seek to use bio-crops as a source of energy and carbon. These have a high energy content (~19MJ/kg), but there is competition with food uses which affects price and availability. Agricultural wastes from harvesting crops such as corn are a much better idea, and these are just part of the huge amount of readily available waste streams that can be used to produce fuel. Surely this is a better idea!
Our unique process
In the Avioxx process the bulk of the energy comes from the residual energy in the waste materials used as feedstock. This can vary widely, for example kerbside residual household waste in the UK consists of about 30% food waste, which tends to contain a lot of water, and has a low energy content, but also quite a lot of paper, board and plastics which have high energy.
The average heat value is estimated at about 13MJ/kg. RDF (Refuse-derived fuel), which is waste which has been shredded and left to dry a little is quoted to have an energy content of about 20MJ/kg. Carbon derived from pyrolysis, a potential waste pre-treatment, has an even higher energy content and starts to approach the energy levels of the fuel (~43MJ/kg) we are aiming to produce. Pre-treating the feedstock to raise its energy value is therefore an important step to consider.
So, the technology we are providing is dealing with the extraction of the energy in the waste feedstock and transferring it into the fuel. Obviously quite a lot of feedstock is needed to produce a tonne of fuel, but the efficiency of the process is of huge commercial significance.
The unique Avioxx process involves the combination of oxygen-based gasification, to break down the pre-treated feedstock, electrolysis to produce the oxygen and energy-rich hydrogen, fuel cell power production and a Fischer-Tropsch polymerisation step to make the fuel itself. This integrated, energy-optimised process has substantial flexibility and redundancy, plus a complex control system to provide stability and precision with little human intervention. Managing the wide variations in waste feedstock quality is a key requirement.
Provision is also made to import and store green electricity to make green hydrogen. This supplements the power generated by the fuel cell system, which is another important point of difference of the Avioxx process.
Energy efficiency and cost-competitiveness
We believe the process to be the most energy-efficient and cost-competitive route to making SAF, combining new technologies with well-established techniques, and very low-cost inputs. We also believe it offers a great opportunity to produce fuels which are better than existing ones in both performance and (non-CO2) environmental impacts.
We will work with the waste management industry to install plants at strategic locations, of the appropriate scale and within reach of the fuel storage, blending and distribution infrastructure. We are also promoting a vibrant and recognisable brand and establishing thought leadership in this rapidly developing sector.
At Avioxx, carbon capture is an important stage of our production process to allow us to achieve carbon net zero fuel. The carbon we capture is used in other areas of our process or if there is a surplus of carbon captured it will be sold or stored appropriately.
If you’d like to learn more about the Avioxx process, how we approach carbon capture and achieve net zero sustainable fuel production then please contact us at info@avioxx.com.