Clean Energy Technology

A double smart grid integrates a smart electricity and district energy network to fully exploit synergies among energy loads (e.g. especially for electricity, heating and cooling needs) and integrate a wide variety of renewable (e.g. PV, solar thermal, Power-to-Heat) or waste energy resources.

The biomass-based Fischer Tropsch pathway (bio-FT) is typically referred to as a biomass-to-liquid (BTL) route, though this umbrella term can apply to any route which produces liquid fuel from biomass. In the bio-FT route, biomass is first gasified into syngas and the syngas is then converted into hydrocarbon liquids via the Fischer-Tropsch process. Biomass with a high lignocellulosic content (e.g. wood, straw, residues from forestry and agriculture, municipal solid waste) is gasified via heating in an oxygen-restricted environment, producing a mixture of mostly hydrogen (H2), carbon monoxide (CO), carbon dioxide (CO2), and other hydrocarbons. This "syngas" is then sent to a water-gas shift (WGS) reactor to increase the H2/CO ratio required for Fischer-Tropsch (FT) synthesis. In the CCUS variant, the CO2 is separated from the syngas prior to FT synthesis, resulting in a pure stream of CO2 that can be captured and compressed for utilisation or storage rather than vented. If stored, negative emissions are created. The resulting liquids from the FT reactor are further cleaned and separated into their hydrocarbon products (diesel, jet, naphtha, wax, etc). Technical challenges revolve around tar buildup and removal during gasification. The biomass used to produce bio-FT are not food crops, avoiding direct competition with food and unwanted land-use change. Fuels resulting from bio-FT are "drop-in" and can therefore use existing fossil fuel infrastructure and technology without blending limits. Technical challenges revolve around tar buildup and removal during gasification. Bio-FT kerosene (biojet) is a American Society for Testing and Materials (ASTM)-certified sustainable aviation fuel (SAF), allowed to be blended up to 50%.

Hydrogenated vegetable oil (HVO) - also known as hydroprocessed esters and fatty acids (HEFA) - is a type of renewable diesel while HEFA is a type of drop-in biokerosene, meaning it is a drop-in fuel and theoretically has no upper blend limit with fossil diesel and kerosene, though it is currently capped at 50% blend for use in aviation. HVO is produced via well-known hydrotreatment commonly used at petroleum refineries. An oil feedstock (vegetable oil such a soybean, palm or rapeseed, or waste oils such as animal fats and used cooking oils) is reacted with hydrogen in the presence of a catalyst to remove oxygen and break the triglycerides in the oil into three separate hydrocarbon chains. When compared to FAME biodiesel, HVO/HEFA has better storage stability, cold flow properties and a higher cetane number (higher ignitibility). HVO/HEFA kerosene/jet fuel is an American Society for Testing and Materials (ASTM)-certified sustainable aviation fuel (SAF) pathway, allowed to be blended up to 50%.

Micro-algae are grown to produce lipids. They can be grown in open ponds, closed photobioreactors, or in heterotrophic bioreactors (no light required). Once the lipids (oils) are extracted from the algae, the process is similar to traditional hydrogenated or hydrotreated vegetable oil (HVO). Hydrogen is added to the oil feedstock in the presence of a catalyst to convert triglycerides into long-chained hydrocarbons that can be considered a renewable diesel (drop-in). The main technical challenge with this technology is producing algae with high lipid content and then extracting the lipids efficiently. A major benefit of algae-based biofuels is their potential to produce biofuels without competition with food, as algae can be grown on non-arable land, though it has high land/nutrient/energy/water usage.

This process integrates several individually well-known steps to convert an alcohol (methanol, ethanol, butanol) into a drop-in renewable diesel or jet fuel. The feedstock alcohol undergoes dehydration to remove water, oligomerisation to create longer chain hydrocarbons out of shorter chains, hydrogenation through the addition to hydrogen to convert the hydrocarbons into desired fuels, and finally distillation to separate the products into diesel, jet fuel and other streams. Alcohol-to-jet (ATJ) is a American Society for Testing and Materials (ASTM)-certified sustainable aviation fuel (SAF), allowed to be blended up to 50%.

The biomass-based Fischer Tropsch pathway (bio-FT) is typically referred to as a biomass-to-liquid (BTL) route, though this umbrella term can apply to any route which produces liquid fuel from biomass. In the bio-FT route, biomass is first gasified into syngas and the syngas is then converted into hydrocarbon liquids via the Fischer-Tropsch process. Biomass with a high lignocellulosic content (e.g. wood, straw, residues from forestry and agriculture, municipal solid waste) is gasified via heating in an oxygen-restricted environment, producing a mixture of mostly hydrogen (H2), carbon monoxide (CO), carbon dioxide (CO2), and other hydrocarbons. This "syngas" is then sent to a water-gas shift (WGS) reactor to increase the H2/CO ratio required for Fischer-Tropsch (FT) synthesis, and CO2 is separated and vented. The syngas is fed into the FT reactor, and the resulting liquid hydrocarbons are cleaned, refined and separated into diesel, jet fuel, naphtha and other products. The biomass used to produce bio-FT are not food crops, avoiding direct competition with food and unwanted land-use change. Fuels resulting from bio-FT are "drop-in" and can therefore use existing fossil fuel infrastructure and technology without blending limits. Technical challenges revolve around tar buildup and removal during gasification. Bio-FT kerosene (biojet) is a American Society for Testing and Materials (ASTM)-certified sustainable aviation fuel (SAF), allowed to be blended up to 50%.

In hydrothermal liquefaction (HTL) (also called catalytic hydrothermolysis, CHJ) , biomass decomposes into gases and bio-oil using water under high pressure (150 to 350 bar) and high temperature (250 - 450 °C), often in the presence of an alkali catalyst. A variety of biomass can be used and the biomass does not need to be dry, an advantage over pyrolysis and other thermochemical conversion processes. The bio-oil is separated from the gaseous and aqueous products, and can then be refined into high quality fuel such as diesel using typical petroleum refining processes. It can be co-fed with fossil-based oil into refineries. As this version of bio-oil has lower oxygen content than pyrolysis oil, it can be blended into heavy fuel oil for use in the shipping industry. HTL with upgrading is a American Society for Testing and Materials (ASTM)-certified sustainable aviation fuel (SAF) pathway, allowed to be blended up to 50%.

Micro-algae are grown to produce lipids. They can be grown in open ponds, closed photobioreactors, or in heterotrophic bioreactors (no light required). Once the lipids (oils) are extracted from the algae, the process is similar to traditional fatty acid methyl ester (FAME) biodiesel production, in which the oil feedstock is reacted with methanol in the presence of a catalyst to produce biodiesel and glycerine. The main challenge with micro-algae is the high cost of cultivation and harvesting (lipid extraction) compared to terrestrial biomass; other issues arise from lipid content, reducing energy/water/nutrient/land footprint, and integrating the full process pathway at demonstration scale. On the other hand, algae can be grown on non-arable land, avoiding competition with food. It can also be grown rapidly, and exhibits high photosynthetic efficiency, potentially leading to greater biofuel per unit area yields compared to terrestrial biomass.

Fatty acid methyl ester (FAME) biodiesel is produced by reacting either vegetable oil (soybean, palm, rapeseed) or waste oils (animal fats, used cooking oils) with methanol in the presence of a catalyst. The transesterification reaction of the triglycerides found within the oils produces biodiesel and glycerine. The biodiesel and glycerine undergo a series of purification and separation steps to clean the final products and to recover the catalyst and any remaining methanol. Glycerine can be sold to the pharmaceutical industry. The biodiesel can be blended up to 5-7% with fossil diesel for use in road transport, or can be blended up to 100% for use in marine diesel engines.

The biomass-based Fischer Tropsch pathway (bio-FT) is typically referred to as a biomass-to-liquid (BTL) route, though this umbrella term can apply to any route which produces liquid fuel from biomass. In the bio-FT route with hydrogen enhancement, biomass is first gasified into syngas (mostly hydrogen, carbon monoxide and carbon dioxide). Instead of sending the syngas to a water-gas shift (WGS) reactor, as is done in the usual bio-FT route, low-carbon hydrogen is added to the syngas to drive a reverse water-gas shift (rWGS) reaction, converting hydrogen (H2) and carbon dioxide (CO2) into water and carbon monoxide (CO). Sufficient hydrogen is added to ensure a desired H2/CO ratio for Fischer-Tropsch (FT) synthesis. The liquids from the FT reactor are further cleaned and separated into their drop-in hydrocarbon products (diesel, jet, naphtha, etc). The benefit of adding hydrogen is a more efficient use of the carbon in biomass, as the carbon in CO2 is converted into hydrocarbon fuels rather than being either vented (bio-FT route) or captured and stored (bio-FT w/ CCS route). Rather than providing negative emissions, the additionally converted carbon can displace fossil carbon within the energy system. Technical challenges revolve around tar buildup and removal during gasification. Bio-FT kerosene (biojet) is a American Society for Testing and Materials (ASTM)-certified sustainable aviation fuel (SAF), allowed to be blended up to 50%.

Micro-algae can be grown in open ponds, closed photobioreactors, or in heterotrophic bioreactors (no light required). Once grown, the whole algae cell is hydrothermally liquefied (HTL) via the same process used for terrestrial biomass. The algal bio-oil is separated from the remaining products and can be sent to hydrotreatment (common in petroleum refineries) to be upgraded to a drop-in biodiesel (renewable diesel). The remaining solids, water and carbon dioxide are treated and recycled to the cultivation step, while remaining off-gases provide heat, electricity or hydrogen. As with all algal biofuel systems, the main challenge arises from the high cost of harvesting and cultivation, as well as reducing the energy/water/nutrient/land footprint of the system. However, algae can be grown on non-arable land, avoiding competition with food. Benefits of using the HTL route with micro-algae include HTL's ability to handle wet feedstocks, and its use of all algae components (lipids, carbohydrates, proteins), removing the need to cultivate high lipid content and extraction.

In pyrolysis, biomass is heated in the absence of oxygen and decomposes into bio-oil and biochar. Fast pyrolysis (on the order of seconds) of dry biomass (up to 10% moisture content) is typically used to produce an output that is mostly bio-oil. Once produced, the pyrolysis bio-oil can then be refined to higher quality fuels such as diesel via standard petroleum refining units (fluid catalytic crackers, hydrocrackers). The bio-oil can be co-fed into refineries with crude fossil-based oil.