Low-energy carbon capture

The generation of biomethane for grid injection into the gas network and for road transportation is a crucial element of the 2030 Climate & Energy Framework and future low carbon strategy. Biogas can be generated using the Anaerobic Digestion (AD) process and historically it has been used to generate heat or electricity via a combined heat and power cycle (CHP).  However, to achieve its maximum potential as a universal renewable fuel it must be purified to “fossil grid” specification (EN 16723).  At Aqua-B, we have developed a NB-enabled technology that will allow for the economic purification of biogas into biomethane for injection into a gas grid – capturing CO2 preferentially in water. We can also capture flue-gas carbon and other pollutants for water-wash and gas-absorption columns.

Opportunity

Currently there are a number of techniques used to separate CO2 from methane, including cryogenic separation, membrane technology, pressure swing adsorption (PSA) and solvent scrubbing. However, these technologies are designed for large volume separation (>1000NM3/Hr) and not for small scale applications. Some of these technologies are reasonably economically efficient for capacities in excess of 300 NM3/Hr and indeed membrane separation and chemical scrubbing technologies are also adequate in excess of 100 NM3/Hr. However, the trend throughout Europe is for smaller (20-200 NM3/Hr) biomethane purification capacities, and this is where the NBF technology offers a competitive and key advantage. The same applies to smaller point emitters of carbon, e.g., smaller cement works. 

Innovation

We purify bio-gas, by generating nano-bubbles using our additive-free and energy-efficient breakthrough patented technology. This is done with the bio- or flue-gas in contact with liquid water (whether batch or continuous mode, or fed-batch, etc). The reason for differential take-up of gas, in nano-bubble (NB) form, into the water is that, even though de-facto methane solubility is around 30 times higher than its Henry’s-Law level in nano-bubble form, this is still very small in terms of mass per volume in water (mg/l) in absolute terms. With CO₂ and H₂S’s conventional (standard molecular-solvation) Henry’s-Law solubilities offering at least 40-50 times higher than CH₄ in terms of absolute mass-per-volume level in water (i.e., in mg/l terms), a ~2-fold increase for CO₂ solubility with NB creation from our breakthrough method leads to much more high absolute level of CO ₂ and H₂S uptake into water – purifying very substantially the methane in a single-pass design. This is explained more in the YouTube videos below.