What Is the Best Feedstock for Biogas? Yield, Cost, and Practical Ranking
The best feedstock for biogas depends on your objective—maximum methane per ton, lowest cost, or easiest handling. Fats, oils, and grease (FOG) and food waste deliver the highest specific yields (up to 1,200–1,500 L CH₄ per kg volatile solids), but manure and agricultural residues win on cost and availability for continuous large-scale supply.
The Yield Hierarchy: Methane per Ton
Specific methane yield scales roughly with how much readily biodegradable carbon a feedstock carries. Energy-dense, low-lignin materials (FOG, food waste, energy crops) sit at the top with 350–1,500 L CH₄/kg VS; fibrous manures and lignocellulosic residues sit lower at 100–400 L CH₄/kg VS because much of their carbon is locked in tough plant cell walls microbes digest slowly.
Comparative Data Table: Feedstock Methane Yield & Practicality
| Feedstock | CH₄ Yield (L/kg VS) | Typical Cost | Practical Notes |
| FOG / fats | 1,200–1,500 | Often paid (collection fee) | Highest yield; needs co-digestion |
| Food waste | 400–600 | Low–negative (gate fee) | High yield; H₂S risk, pasteurization |
| Energy crops (maize silage) | 350–500 | Medium (land cost) | Reliable; sustainability debate |
| Poultry manure | 250–400 | Low | N-rich; co-digest with carbon |
| Cattle manure | 150–250 | Very low (on-farm) | Low yield; stable base load |
| Ag residues / straw | 100–250 | Low | Seasonal; lignocellulosic |
The Verdict: Best Feedstock by Objective
Best specific yield → FOG and food waste, because their energy density is unmatched. Best cost → on-farm manure, where the feedstock is free and the alternative (lagooning) is a liability. Best balance for a commercial plant → food waste collected under a gate fee plus co-digested with manure or energy crops to stabilize the carbon-to-nitrogen ratio and avoid ammonia inhibition.
Why Co-Digestion Beats a Single Feedstock
Almost no single feedstock is ideal alone. Food waste is nitrogen-rich and can inhibit at high load; manure is carbon-poor and low-yield; straw is too fibrous. Mixing 2–3 streams lets you hit the optimal C:N ratio of 20–30:1, smooth seasonal supply gaps, and lift total yield 10–30% above any single stream—which is why 70%+ of commercial plants co-digest.
Frequently Asked Questions (FAQ)
Q1: Which feedstock gives the highest biogas yield?
A: Fats, oils, and grease (FOG) top the chart at 1,200–1,500 L CH₄ per kg volatile solids, followed by food waste at 400–600 L. Both must be co-digested with lower-fat material, because pure FOG can acidify the digester and stall methane production.
Q2: What is the cheapest feedstock for biogas?
A: On-farm manure is effectively free and beats any purchased substrate on cost. For off-farm commercial plants, food waste and organic industrial residues accepted under a gate fee (where you are paid to take them) are the cheapest net-cost feedstocks, often negative $5–30 per tonne.
Q3: Is food waste better than manure for biogas?
A: For yield per ton, yes—food waste produces 2–3x more methane than cattle manure. For reliability and cost, manure is better as a stable base load. The smart answer is both: manure as the consistent backbone, food waste as the high-yield booster.
Q4: Can you mix feedstocks for better biogas?
A: Absolutely, and you should. Co-digestion balances the C:N ratio, diversifies supply risk, and typically raises total methane 10–30% versus a single stream. The main rule is to introduce new feeds gradually (10–20% steps) so the microbial community adapts without shock.