Bioenergy

Rudolf Diesel developed his compression-ignition engine during the 1890s, with the first successful model completed in 1897. At the 1900 Paris Exposition, a small Diesel engine built by the French Otto Company was demonstrated running on peanut oil at the request of the French government. The engine had been designed for ordinary oils but operated on vegetable oil without modification.

Biomass and biofuels can be stored for long periods and used whenever energy is needed, giving countries energy security throughout the year. However, this is dependent on the type of biofuel, and there are exceptions. Storage life varies considerably by fuel, formulation and storage conditions, and some biofuels are much less stable than others ^{[58-64,66,68]}.

For example, wood pellets and other solid biomass are particularly affected by moisture, temperature, ventilation and handling. Poor conditions can cause biological degradation, loss of energy content or self-heating, while dry and properly ventilated storage can preserve their quality ^[60,61].

A long-term biofuel such as HVO (Hydrotreated Vegetable Oil) has high resistance to oxidation and can reportedly last around 10 years before it degrades according to suppliers, assuming appropriate storage conditions are maintained ^A. Independent research also supports HVO’s relatively high stability, including when it is incorporated into biodiesel - diesel blends ^[64]. The stability of FAME (fatty acid methyl esters) biodiesel depends heavily on its fatty-acid composition: saturated FAMEs are generally more stable and will last longer than unsaturated FAMEs, depending on the waste used to create them. Therefore, the original feedstock used to create the biofuel can significantly affect storage life ^[62,63].

Although biodiesel is readily biodegradable, deterioration during storage is primarily caused by oxidation and contamination rather than biodegradability itself. Heat and exposure to air, light, water or certain metals can accelerate degradation, while antioxidants and suitable storage conditions can slow it ^[58,62,63]. One study reports that biodiesel has a storage capacity of 6 months before degradation begins, and after a year it may no longer be suitable for direct use in engines ^[58,59].

Creating blends of biofuels (e.g. mixing FAME biodiesel with petroleum diesel or HVO) can improve stability, increase storage durations as well as maintain their effectiveness as a drop-in fuel for standard engines, although the result depends on the fuels and proportions involved ^{[58,59,62,64]}.

Specially formulated nano-biodiesels are enhanced with nanoparticles that reduce vulnerability to oxidation, and so can remain stable for much longer ^[59]. They can also improve fuel combustion and energy efficiency while also reducing some pollutants. However, their effects depend on the material, concentration, fuel and engine, and some formulations can increase nitrogen-oxide emissions ^B.

Biofuels have shorter shelf-lives than regular fossil fuels (but HVO is a notable exception). Nevertheless, they can still help to address the intermittency problem created by wind/solar energy: even biofuels stored for months instead of years can provide readily dispatchable backup power and energy security over periods of low wind or solar generation, provided sufficient stocks and equipment are available ^[23,66,68]. Where feedstocks and supply chains are sustainably managed, they can contribute towards carbon neutrality and wider emissions-reduction efforts ^{[19-22,72-76]}.

^A How to Store HVO Fuel for Longevity and Safety | Vectec

^B Applications of nanotechnology in biodiesel combustion and post-combustion stages | Renewable and Sustainable Energy Reviews

Bioenergy is not automatically carbon neutral. Its climate impact depends on the feedstock, regrowth, what would otherwise have happened to the land or material, supply-chain emissions and the time required to reabsorb the released CO₂. Waste and residue pathways can have relatively low emissions, while land-use change or harvesting slowly regrowing forests can create a carbon debt lasting years or decades.

See: Carbon Accounting for Sustainable Biofuels - Analysis | IEA

In Brazil, millions of hectares of rainforest, savanna and other native ecosystems have been cleared for agricultural purposes, including soybean and sugarcane production.

Trase associated Brazil’s 2020 soy harvest with 562,000 hectares - 5,620 square kilometers - of recent deforestation and native-vegetation conversion. This included approximately 76,400 hectares in the Amazon and 23,600 hectares in the Atlantic Forest, although most occurred in the Cerrado and Pampas. The Cerrado biome, a key area for soy and sugarcane, has experienced particularly extensive land conversion ^[82,83]. These figures connect Brazilian soy production with land conversion measured in thousands of square kilometers, including substantial areas of rainforest.

Both soy and sugarcane are connected to Brazil’s biofuel industry ^[78,80,81]. Approximately half of Brazil’s sugarcane is processed into ethanol ^C. Soybeans are primarily grown for animal feed, but they produce soybean oil as a by-product which provides around 70% of the country’s biodiesel ^D. Across South America, the area planted with soy more than doubled from 26.4 million hectares in 2000 to 55.1 million hectares in 2019 ^[82]. Expansion of these crops can drive deforestation directly, where crops replace native vegetation, or indirectly, where expansion onto existing agricultural land displaces cattle grazing or other activities into newly cleared areas ^[78-82,84].

Soybean-related deforestation in Brazil is considerably larger than direct clearance for sugarcane ^[80-83]. From 2009, the Sugarcane Agroecological Zoning (ZAE Cana) policy restricted sugarcane expansion in critical biomes like the Amazon and Pantanal (although the policy was repealed in 2019, increasing concerns about deforestation) ^[81]. Sugarcane cultivation has therefore historically been concentrated in central and southern regions outside the Amazon, often on existing agricultural land, degraded pasture or the Cerrado. Its direct contribution to Amazon rainforest loss is therefore much smaller than that of cattle or soy. Nevertheless, its expansion into the Cerrado or onto pasture can replace native vegetation or displace other agricultural activities, contributing to wider deforestation pressures ^[78,80,81]. In fact, one 2010 modelling study projected that sugarcane-ethanol expansion could have indirectly contributed to around 50,000 km² (5 million hectares) of deforestation by 2020, largely by displacing cattle pasture towards forested areas ^[85].

Biofuel demand can therefore contribute to deforestation by increasing demand for sugarcane ethanol and soybean oil for biodiesel. However, the entire affected area cannot be attributed specifically to biofuels: soy also supplies animal feed and food products, sugarcane also supplies sugar, and much of the converted vegetation is savanna or grassland rather than rainforest. Nevertheless, given the scale of soy-related conversion and the direct and indirect effects associated with both crops, it remains a reasonable order-of-magnitude estimate that thousands of square kilometers of Brazilian rainforest have been cleared partly to supply biofuel crops, if not a precise biofuel-only total ^[78-84].

^C Brazil’s sugarcane allocation between sugar and ethanol | Reuters

^D Around 70% of Brazilian biodiesel comes from soybeans | Reuters

Additional reading:

In Brazil, a Sugarcane Rush Poses a New Threat to the Amazon Rainforest | Sierra Club

Brazil sugarcane growth can meet biofuel need and not drive deforestation: study | Mongabay

CORRECTION: Around 55% of European airlines’ publicly announced SAF commitments and supply agreements are expected to come from used oils and fats, including animal fats, used cooking and other waste oils. This describes agreements and planned contracts, rather than fuel already in use as stated in the video.

BECCS can produce net-negative emissions only when biomass regrowth genuinely removes atmospheric CO₂, and more of that CO₂ is permanently stored than is released across the entire process. In reality, this depends on more than the emissions produced at the bioenergy facility. It also depends on supply-chain and land-use emissions and long-term carbon balances involved. This includes carbon lost from vegetation and soils; the time required for biomass to regrow; emissions from cultivation and fertilizers, harvesting, processing, transport; the energy used to capture, compress and inject the CO₂, and any CO₂ that the capture system does not collect. Other greenhouse gases, such as methane and nitrous oxide, must also be included. The final balance therefore depends on the feedstock, land management, capture rate, energy sources and timeframe considered ^{[72-76,97-102,118-121]}.

For long-term storage, captured CO₂ is normally compressed and injected into deep, porous rock formations, such as saltwater formations or depleted oil and gas reservoirs. In reality, the CO₂ occupies tiny spaces within the rock rather than simply filling a large underground cavern or mine shaft. Careful site selection, secure wells, pressure management, monitoring and long-term oversight are essential to keeping it contained ^{[118,127,128]}.

The main leakage concern is captured CO₂ escaping during transport or injection, or later through faults, fractures or damaged or poorly sealed wells. Evidence in [125-128] largely concerns possible leakage pathways, controlled experiments, modeling and risk assessment; it does not indicate that leakage is common at well-managed commercial storage sites. Properly selected and monitored geological formations are expected to retain almost all injected CO₂ for very long periods, although the risk cannot be treated as zero. Any CO₂ that escapes must be subtracted from the claimed total removed from the atmosphere and addressed through continued monitoring and remediation.

Microalgae can be cultivated in open ponds or enclosed photobioreactors on non-arable, degraded, saline or otherwise low-value land, avoiding direct competition with conventional food crops. Suitable sites still require sufficient light, water, nutrients and CO₂, while the amount of land needed depends on the algae species, local climate and cultivation system. Because algae grow rapidly and can produce more fuel per unit of land than conventional biofuel crops, their overall land requirements can be considerably lower ^[129-134].

Seaweed requires neither farmland nor freshwater. Seaweed farms can create temporary habitats for fish and invertebrates, absorb excess nutrients, raise local oxygen and pH levels, and reduce wave energy. The biodiversity benefits depend on the species grown, farm size and layout, water movement, location and harvesting practices. Careful siting can maximize these benefits while avoiding damage to existing habitats such as seagrass beds or introducing non-native species ^[135-140].

Microbial fuel cells use bacteria to break down organic matter in wastewater and transfer the released electrons to an electrode, creating an electrical current. Removing this organic matter helps clean the wastewater, although MFCs do not normally provide every stage of treatment by themselves: further treatment may still be required to remove remaining organic material, nutrients and pathogens ^[141-144].

In reality, their main economic benefit may come from reducing the electricity required for treatment rather than generating large amounts of surplus power that can be used elsewhere. Conventional wastewater treatment uses considerable energy to pump oxygen into the water. MFCs can reduce some of this aeration while recovering a small amount of the wastewater’s chemical energy as electricity, potentially lowering the treatment plant’s overall energy demand. Together, these benefits could ultimately make wastewater treatment cheaper. For now, however, high construction and material costs mean that this has not yet been demonstrated consistently at commercial scale ^[141-143].

Reaching that point may not require MFCs to maximize electricity output. In other words, the system that produces the most electricity is not necessarily the most economical treatment system. One techno-economic study found that less expensive electrode materials could provide more cost-effective wastewater treatment despite producing less electricity ^E. This suggests that practical MFC development may benefit from prioritizing affordable treatment over maximum electrical output.

However, electricity output remains low, particularly as the wastewater becomes cleaner and less organic material remains for the bacteria to consume. Larger systems must also overcome electrode and membrane costs, fouling, uneven performance and long-term reliability. A 1,000-liter pilot study has demonstrated that the technology can operate with real municipal wastewater, but it achieved partial treatment and modest electricity generation. For now, therefore, MFCs remain primarily an experimental method of combining wastewater treatment with small-scale energy recovery, rather than a major source of electricity ^[141-144].

^E Sacrificing power for more cost-effective treatment: A techno-economic approach for engineering microbial fuel cells | Chemosphere