The Downsides of Biofuels: Risks That Complicate a “Green” Alternative

Biofuels can cut fossil fuel use in some sectors, but they come with substantial drawbacks: land-use change and biodiversity loss, uncertain climate benefits for many feedstocks, competition with food production, heavy water and fertilizer demands, air-pollution trade-offs, infrastructure and engine constraints, high costs and scalability limits, and complex, sometimes flawed policy accounting.

Why the cons of biofuels matter now

Biofuels include first-generation fuels from food crops (corn ethanol, sugarcane ethanol, soy and palm biodiesel), and advanced fuels made from wastes, residues, cellulosic biomass, or algal pathways, as well as aviation-focused sustainable aviation fuel (SAF). While some pathways perform better than others, a growing body of research and recent policy debates underline that many biofuels—especially crop-based options—carry material environmental, economic, and social downsides that can blunt or even negate their intended climate benefits.

Environmental and climate drawbacks

The following points summarize the key environmental risks and climate-limitations associated with biofuels across their life cycle, from cultivation and processing to combustion.

• Land-use change and “carbon debt”: Expanding cropland for biofuel feedstocks can drive deforestation, peatland drainage, and grassland conversion, releasing large stores of carbon. This “carbon debt” can take years to decades to repay, especially for high-risk feedstocks like palm oil or soy linked to forest loss.
• Biodiversity loss: Converting diverse habitats into monocultures reduces species richness, fragments ecosystems, and threatens pollinators and soil biota essential for long-term agricultural resilience.
• Uncertain net GHG benefits: Life-cycle emissions vary widely. Fertilizer use emits nitrous oxide (a potent greenhouse gas), and processing can rely on fossil energy. Methane from palm oil mill effluent and soil carbon losses can erode expected savings, making some crop-based fuels only marginally better—or sometimes worse—than petroleum.
• High water demand and pollution: Irrigated feedstocks (e.g., sugarcane) stress water-scarce regions. Runoff of fertilizers and pesticides leads to eutrophication and dead zones; processing facilities also consume and contaminate water if not well managed.
• Soil degradation: Intensive cultivation and residue removal for cellulosic feedstocks can deplete soil organic carbon, increase erosion, and reduce long-term fertility without careful agricultural practices.
• Air-quality trade-offs: While some pollutants drop, others can increase. Ethanol blends can raise acetaldehyde emissions; biodiesel often reduces particulate matter but can increase NOx, contributing to smog. Incomplete combustion of solid biomass (for heat/cooking) remains a major source of harmful PM2.5 in many regions.

Taken together, these factors mean biofuels are not automatically “low-carbon”; their real-world impact hinges on feedstock choice, land-use history, farming practices, and processing energy sources.

Food, land, and social impacts

Beyond ecology and climate, biofuels can affect food systems and communities, particularly where land rights are weak and markets are volatile.

• “Food vs. fuel” pressures: Diverting crops like corn, soy, and vegetable oils to fuel tightens global supplies, contributing to price spikes and volatility—effects that can intensify during droughts, conflicts, or trade disruptions.
• Land tenure and human rights risks: Large-scale plantations have been linked to disputed land acquisitions, displacement of smallholders, and labor abuses in some producer countries.
• Rural equity concerns: While markets promise new income streams, benefits can concentrate among large agribusinesses; small farmers may face price instability, input-cost burdens, and contract dependencies.
• Water conflicts: Expanding irrigated feedstocks can heighten competition for scarce water, exacerbating tensions among agricultural, urban, and ecological users.

These social dimensions mean biofuel expansion can carry significant human and development consequences unless robust safeguards and inclusive planning are in place.

Technical and operational drawbacks

Even when environmental criteria are met, biofuels pose practical constraints for vehicles, engines, and fuel systems.

• Lower energy content and variable EROI: Ethanol has about one-third less energy per liter than gasoline, reducing fuel economy; energy return on energy invested can be modest for some pathways.
• Compatibility and “blend walls”: High-ethanol blends require compatible engines and fueling infrastructure; ethanol’s hygroscopic nature complicates pipeline transport. Biodiesel’s cold-flow properties can cause gelling and filter clogging in low temperatures.
• Warranty and performance concerns: Many legacy vehicles, small engines, and marine equipment are not certified for higher blends, raising liability and maintenance issues.
• Quality and storage issues: Feedstock variability and oxidation stability (especially for biodiesel) can impair fuel quality; microbial growth and water contamination add handling costs.
• Scalability limits for advanced fuels: Truly low-ILUC feedstocks like agricultural residues, municipal solid waste, and used cooking oil are finite; commercial-scale cellulosic and algal fuels have faced cost and technology hurdles.

These constraints keep many markets anchored to low blend ratios and add costs to distribution and fleet management.

Economic and policy risks

Biofuels operate within policy-heavy markets, where accounting choices and subsidies strongly influence outcomes.

• Subsidy dependence and fiscal cost: Many pathways are not cost-competitive without mandates, tax credits, or carbon credits; abrupt policy shifts can strand investments.
• Accounting controversies: Treating biogenic CO2 as zero at the tailpipe can mask upstream emissions; indirect land-use change (ILUC) is difficult to measure and not always fully priced; book-and-claim systems for SAF create traceability concerns.
• Market distortions and trade tensions: Mandates and tariffs can spur disputes, anti-dumping cases, and supply gluts or shortages, with knock-on effects for food and feed markets.
• Opportunity costs: Land, capital, and policy attention devoted to crop-based biofuels may deliver less decarbonization per dollar than alternatives such as electrification, efficiency, reforestation, or solar/wind on marginal lands.
• Feedstock volatility: Weather shocks, disease, and geopolitical events (e.g., war-driven vegetable-oil price spikes) can rapidly shift economics and availability.

These uncertainties complicate long-term planning and can dilute the climate value per unit of public spending.

Where the drawbacks are smaller—and the limits

Waste- and residue-based fuels (e.g., used cooking oil, animal fats, agricultural residues), genuine cellulosic biofuels powered by low-carbon process energy, and captured-biogas upgrading tend to avoid the worst land-use and biodiversity harms. However, these feedstocks are limited in volume, face quality and fraud risks without strong verification, and remain costlier than fossil fuels in many markets. As a result, they are best viewed as niche solutions for hard-to-electrify uses—particularly aviation—rather than broad substitutes for petroleum across the economy.

Recent policy context

Regulators have increasingly tried to curb the risks: the European Union’s latest renewable energy rules cap or phase down high-ILUC-risk crop-based biofuels and set tighter sustainability criteria; the United States has updated Renewable Fuel Standard volumes and introduced tax credits tied to life-cycle carbon intensity, amid ongoing debate over which models and feedstocks qualify; and aviation policies (CORSIA internationally and ReFuelEU in Europe) are steering demand toward waste/residue-based SAF and e-fuels. Even so, concerns persist over ILUC treatment, verification of used cooking oil and other waste streams, and the true climate value claimed by some pathways.

Summary

Biofuels can help in specific niches, but their downsides are significant: potential land and biodiversity damage, uncertain net climate gains for many crop-based pathways, water and soil impacts, air-pollution trade-offs, technical and infrastructure hurdles, and heavy reliance on complex policies. Waste- and residue-based fuels mitigate many risks but are limited in scale. For broad decarbonization, most analyses favor prioritizing efficiency and electrification, reserving the most sustainable biofuels for hard-to-electrify sectors where alternatives are scarce.