Clean Energy Technology

Also known as the "sugars to hydrocarbons" route, this pathway converts sugars from biomass directly into hydrocarbons similar to diesel and jet fuel. Biological routes use micro-organisms to perform the conversion, while catalytic routes use catalysts under high temperature conditions. Synthetic Iso-Paraffins is an American Society for Testing and Materials (ASTM)-certified sustainable aviation fuel (SAF), allowed to be blended up to 10%.

During the fermentation step, a pure stream of CO2 is emitted that can be captured and compressed at relatively low cost due to the high purity of the stream. As the captured CO2 is biogenic, it can provide negative emissions if it is subsequently stored. This can help offset CO2 emissions in other parts of the energy system. See non-CCUS variant for more detail.

Similar to anaerobic digestion of non-algae feedstock, except that the feedstock is either the remnants of micro-algae after lipid extraction or macro-algae (seaweed). The bacteria break down the algae without oxygen and in the process produce biogas, composed mostly of methane (50-75%) and carbon dioxide (25-45%). Biomass can be in the form of animal manure, organic portion of municipal solid waste (MSW), industrial waste such as dry distillers grain (DDG) from ethanol production, agricultural residues and energy crops. The biogas can be burned directly, without upgrading to biomethane.

In an anaerobic digestor, bacteria break down to biomass without oxygen and in the process produce biogas, composed mostly of methane (50-75%) and carbon dioxide (25-45%). Biomass can be in the form of animal manure, organic portion of municipal solid waste (MSW), industrial waste such as dry distillers grain (DDG) from ethanol production, agricultural residues and energy crops. The biogas is upgraded by removing CO2 and other impurities such as hydrogen sulphide, producing what is commonly referred to as biomethane. Biomethane can be used directly or injected into the gas grid if it meets the required specifications. In some cases, biomethane needs to be mixed with LPG to increase its calorific potential before being injected.

During the fermentation step, a pure stream of CO2 is emitted that can be captured and compressed at relatively low cost due to the high purity of the stream. As the captured CO2 is biogenic, it can provide negative emissions if it is subsequently stored. This can help offset CO2 emissions in other parts of the energy system. See non-CCUS variant for more detail.

Bioethanol from sugar and starch crops is considered a conventional (first generation) biofuel. Carbohydrates (sugars) are enzymatically fermented into ethanol, producing a liquid biofuel that can be blended up to 15% with gasoline for any gasoline engine, and up to 85% for flex fuel vehicles, and 95% for dedicated (compression ignition) ethanol engines. However, in addition to challenges around blend limits, there are sustainability concerns with using food crops for ethanol production, which can lead to competition with food and undesirable land use change.

In an anaerobic digestor, bacteria break down to biomass without oxygen and in the process produce biogas, composed mostly of methane (50-75%) and carbon dioxide (25-45%). Biomass can be in the form of animal manure, organic portion of municipal solid waste (MSW), industrial waste such as dry distillers grain (DDG) from ethanol production, agricultural residues, and energy crops. The biogas can be burned directly, without upgrading to biomethane.

Renewable hydrogen (from renewable-powered water electrolysis) is combined with raw biogas from anaerobic digestion to produce methane via biological conversion. Micro-organisms convert the CO2 in raw biogas and the H2 to biomethane via hydrogenotrophic methanogenesis, avoiding the need to vent or capture the CO2 in the biogas. The biological methanation can occur either within the anaerobic digester, or in a separation reactor. Biological methanation is more resilient to feed gas impurities.

Lignocellulosic ethanol via enzymatic fermentation is an advanced (second generation) biofuel where lignocellulosic biomass is broken down into sugars via enzymatic hydrolysis. From there, the fermentation process to produce ethanol is the same as conventional (first generation) ethanol production. Though more expensive than conventional ethanol, lignocellulosic ethanol uses a biomass feedstock that is considered residue and therefore does not have direct competition with food resources. Like conventional ethanol, its drawbacks are ethanol blend limits with gasoline (15% for use in gasoline engines, 85% for use in flex fuel vehicles, and 95% for use in compression ignition engines).

Syngas (a mixture of mostly hydrogen [H‚ÇÇ], carbon monoxide [CO], and carbon dioxide [CO‚ÇÇ]) is fermented to ethanol and other biofuels (e.g. butanol, acetic acid, etc.) using micro-organisms that function as bio-catalysts. Syngas can be produced via multiple routes, including gasification of biomass with high lignocellulosic content (e.g. wood, straw, residues from forestry and agriculture, municipal solid waste) and via heating in an oxygen-restricted environment. Syngas can also be produced using off-gases from industrial processes like iron and steel manufacturing. However, when using fossil-derived syngas, the emissions reductions potential tend to be lower than using renewable sources of syngas.

Similar to biomethane production from anaerobic digestion, with the addition of a CO2 capture and compression unit integrated into the CO2 separation inherent to biogas upgrading. If the CO2 is stored, negative emissions are created that can offset hard-to-abate emissions elsewhere in the energy system. Larger digestors (> 5 MW) are suitable for carbon capture and storage (CCS) to justify the additional capital expense. See non-CCUS variant for more detail.

Similar to biomethane production from anaerobic digestion, with the addition of a methanation step to further convert the carbon content in the biogas CO2 to methane rather than venting or capturing the CO2. The CO2 is reacted with hydrogen in the presence of a catalyst. The benefit is a more effective use of biogenic carbon present in biogas, which can displace fossil-derived methane.