Biofuels: Weighing the Pros and Cons

Biofuels can reduce lifecycle greenhouse-gas emissions, diversify energy supply, and turn wastes into useful fuel, but their benefits vary widely by feedstock and production method, and downsides include land-use change, competition with food, pollutant trade-offs, lower energy density, infrastructure and engine constraints, and limited sustainable scale. This article explains where biofuels help, where they fall short, and how policy and purchasing choices can maximize benefits while minimizing harm.

What Biofuels Are—and Where They’re Used

Biofuels are liquid or gaseous fuels made from biological material. Common types include ethanol (mostly blended into gasoline), biodiesel (fatty acid methyl esters), renewable diesel (hydrotreated vegetable oil), biomethane/biogas, and sustainable aviation fuel (SAF). “First-generation” biofuels use food crops like corn, sugarcane, soy, rapeseed, and palm; “advanced” or “second/third-generation” fuels use residues, waste oils, non-food cellulosic material, or algae. The climate and air-quality performance of biofuels depends strongly on the feedstock, land-use effects, farming inputs, and processing technologies.

Advantages of Biofuels

The following points summarize commonly cited advantages of biofuels across transportation sectors, noting that the magnitude of each benefit depends on feedstock choice and production practices.

• Lower lifecycle greenhouse-gas emissions versus fossil fuels in many cases, especially for sugarcane ethanol, waste-oil renewable diesel, biomethane, and several SAF pathways. Some pathways achieve 60–90% reductions; benefits are smaller or uncertain for certain crop-based fuels and can be negated by land-use change.
• “Drop-in” compatibility for some fuels. Renewable diesel and many SAFs are chemically similar to petroleum fuels and can be used in existing engines and pipelines without blend limits, easing deployment.
• Air-quality gains in specific contexts. Biodiesel and renewable diesel can cut particulate matter and carbon monoxide; ethanol blends reduce certain aromatics in gasoline. Net effects depend on engine calibration and blend level.
• Energy security and rural development. Domestic production diversifies supply, supports farm and forestry economies, and can reduce import dependence.
• Waste-to-fuel opportunities. Using residues, municipal solid waste, used cooking oil, manure, and sewage sludge turns liabilities into energy, often with high GHG benefits.
• Decarbonization of hard-to-electrify segments. Aviation, some marine routes, and remote/off-road applications currently have few options beyond liquid fuels; SAF and renewable diesel are near-term tools.
• Potential for carbon capture integration. Some facilities (e.g., ethanol plants) can capture fermentation CO2, improving lifecycle performance when stored rather than used for enhanced oil recovery.

Taken together, these advantages make biofuels a pragmatic bridge for sectors where electrification is slow, provided sustainability safeguards steer demand toward the best-performing pathways.

Disadvantages and Risks

These drawbacks are the main reasons biofuels remain controversial, and why their use is increasingly being targeted to the most appropriate applications.

• Land-use change and biodiversity loss. Converting forests, peatlands, or grasslands to grow fuel crops releases carbon and harms ecosystems; this “indirect land-use change” (ILUC) can erase or reverse climate benefits.
• Food-versus-fuel trade-offs. Diverting food crops to fuel can tighten global markets, contributing to price volatility and social impacts, especially during poor harvests or geopolitical shocks.
• Uncertain lifecycle accounting. Emission results vary with modeling choices (e.g., ILUC, fertilizer nitrous oxide, process energy). Some corn ethanol and palm-based pathways show small or negative benefits when broader effects are included.
• Air pollutant trade-offs. While particulates can fall, biodiesel may raise NOx in some engines; ethanol blends can increase acetaldehyde emissions. Local air-quality outcomes depend on technology and fuel blend.
• Lower energy density and efficiency. Ethanol has about two-thirds the energy of gasoline per liter; vehicles consume more volume for the same miles. Biodiesel has slightly lower energy density and poorer cold-flow properties than diesel.
• Engine and infrastructure constraints. Higher ethanol blends (e.g., E15/E85) require compatible vehicles; small engines and older cars may face material and drivability issues. Biodiesel above B20 can cause filter clogging and microbial growth; ethanol’s water affinity complicates pipeline transport.
• Water use and agricultural impacts. Irrigation demand, fertilizer runoff, and soil depletion can be significant for some crop systems, affecting watersheds and emitting nitrous oxide.
• Limited sustainable feedstock supply. Truly low-carbon, waste-based inputs are scarce; rapid demand growth risks displacement effects and fraud in waste-oil supply chains.
• Cost and policy dependence. Many pathways rely on mandates, tax credits, or low-carbon fuel standards; costs for SAF remain 2–5× higher than fossil jet fuel in many markets.
• Transition risks. As road transport electrifies, long-term demand for road biofuels may fall, creating stranded-asset risk and competition with aviation for limited waste lipids.

These risks underscore the need for strict sustainability criteria, robust traceability, and careful targeting of biofuel use to applications where alternatives are weakest.

How Pros and Cons Vary by Feedstock and Generation

First-Generation: Food Crops

Corn ethanol typically shows modest GHG reductions versus gasoline when land-use change is excluded, but benefits can shrink or reverse once ILUC and fertilizer emissions are accounted for. Sugarcane ethanol performs better—often large reductions—given high yields and bagasse-fueled processing. Soy and rapeseed biodiesel can deliver moderate reductions but carry ILUC risks, while palm-based fuels are especially sensitive to deforestation and peatland impacts.

Advanced and Waste-Based: Residues, Cellulosic, Wastes

Biofuels from agricultural and forestry residues, municipal waste, manure, used cooking oil, tallow, and cellulosic feedstocks usually offer higher, more reliable GHG cuts and avoid direct food competition. Commercialization of cellulosic ethanol has been slower than hoped, but renewable diesel and SAF from waste lipids have scaled quickly—constrained by feedstock availability. Policy in many regions now channels incentives toward these pathways and caps crop-based volumes.

When Biofuels Make the Most Sense

The contexts below are where biofuels tend to deliver the strongest net benefits today, based on technology readiness and lifecycle performance.

• Aviation and some marine routes, using certified SAF with robust sustainability criteria.
• Heavy-duty and municipal fleets using renewable diesel as a drop-in, especially where waste-based feedstocks are available.
• Regions with abundant genuine waste and residue streams (landfills, manure, forestry residues) for biomethane or waste-derived liquids.
• Short-to-medium term use in existing internal combustion fleets, while zero-emission alternatives scale.
• Programs that apply strict certifications (e.g., ISCC, RSB) and ILUC safeguards to avoid high-risk feedstocks and practices.

Focusing demand in these niches maximizes climate benefits per unit of limited sustainable feedstock and avoids the most contentious impacts.

Practical Guidance for Policymakers and Buyers

The following actions can help capture benefits while reducing unintended consequences across supply chains.

1. Prioritize waste- and residue-based pathways and set declining caps on food-crop biofuels.
2. Require traceability and independent certification to prevent fraud and ensure land-use safeguards.
3. Evaluate full lifecycle emissions, including ILUC, fertilizer nitrous oxide, process energy, and co-product accounting.
4. Pair biofuel mandates with conservation, reforestation, and soil-health programs to protect carbon stocks and biodiversity.
5. Support R&D and commercialization for cellulosic and algae pathways; improve enzymes, pretreatment, and yield.
6. Match blends to engine certifications (e.g., E10/E15/E85, B20, or drop-in fuels) and manage cold-flow and storage issues.
7. Monitor local air quality impacts and adjust blends or aftertreatment strategies to control NOx and aldehydes.
8. Plan for convergence with electrification—reserve scarce low-carbon liquids for aviation and other hard-to-electrify uses.

These steps align incentives with real climate outcomes, reduce market distortions, and maintain public confidence in biofuel programs.

Bottom Line

Biofuels are not a monolith. When made from wastes and residues, used in the right sectors, and governed by strong safeguards, they can deliver meaningful emissions cuts and energy security benefits. When they drive land conversion, compete with food, or displace better alternatives, their promise fades. The most durable strategy is to target limited sustainable biofuels to aviation and other hard-to-electrify niches, while accelerating electrification and efficiency elsewhere.

Summary

Advantages: potentially lower lifecycle emissions, drop-in options for some fuels, air-quality improvements in certain engines, energy security, and waste reduction—especially for waste- and residue-based pathways. Disadvantages: land-use change and biodiversity loss, food competition, uncertain lifecycle results, pollutant trade-offs, lower energy density, compatibility and infrastructure limits, water and fertilizer impacts, limited sustainable feedstocks, and cost reliance on policy. Effective policy now favors advanced, waste-based biofuels, caps crop-based volumes, and reserves scarce low-carbon liquids for hard-to-electrify sectors like aviation.