Less Waste Underground, More Climate Gains: The Economics of Mexico’s Landfill Methane Recovery

A study of Mexico's Cuernavaca metropolitan area suggests that using this gas for electricity could cut the modeled landfill's climate emissions by nearly 72%, with the benefits depending heavily on how effectively the gas is captured.

Food scraps and paper buried in a landfill keep breaking down after the rubbish trucks leave, releasing methane that can escape into the atmosphere or be collected as fuel. A study of Mexico's Cuernavaca metropolitan area suggests that using this gas for electricity could cut the modeled landfill's climate emissions by nearly 72%, with the benefits depending heavily on how effectively the gas is captured.

Published in the journal Waste, "Landfill Gas Valorization for Electricity and Carbon Credits in a Mid-Sized Mexican Metropolitan Area" examines a proposed regional landfill serving ten municipalities. Researchers led by Roberto Flores compared burning captured gas in enclosed flares with generating electricity, testing how waste composition, equipment choices, electricity prices and carbon-credit rules influence the outcome.

How Much Energy Is Hidden in the Waste

The planning scenario assumes ten years of waste disposal, from 2024 to 2033, with gas recovery assessed through 2044. A starting population of roughly 1.14 million produces about 0.88 kilograms of rubbish per person daily. If every tonne reached the landfill, cumulative disposal would total 3.93 million tonnes, an upper estimate because collection gaps and recycling reduce the amount actually buried.

Using standard settings in the US Environmental Protection Agency's LandGEM model, the researchers calculated around 265,000 tonnes of methane and 1.12 million megawatt-hours of electricity over 21 years. Parameters reflecting regional waste composition and climate reduced methane to 151,000–185,000 tonnes and electricity to 640,000–780,000 megawatt-hours. Food-rich local waste has a lower methane yield per wet tonne and decomposes faster than the standard model assumes. The regional estimates required smaller plants of 8–10 megawatts.

Capturing Gas Early Determines the Climate Gains

The calculations track gas that escapes collection, methane consumed by bacteria in the soil cover, and unburned methane leaving equipment. Electricity comes only from methane actually burned. Carbon dioxide released from decomposing organic material is treated as biogenic, avoiding double counting that can distort comparisons between flaring and energy recovery. Accounting for incomplete collection produced lower reductions than calculations assuming every unit of gas reaches the equipment.

At 75% collection efficiency, enclosed flaring reduced greenhouse emissions by 66.7% against uncontrolled gas release. Electricity generation increased that reduction to 71.8%, avoiding about 4.63 million tonnes of carbon dioxide equivalent. Its advantage over flaring was 5.1 percentage points, partly because the conservative engine assumption allowed 13% of incoming methane to escape unburned. Cutting this methane slip to 1% raised the modeled reduction to 82.8%. A scenario with a progressively cleaner electricity grid reduced the base benefit to 69.7%, still above flaring.

Collection performance had the strongest influence on the percentage of emissions avoided: electricity generation achieved reductions of 47.9% at 50% capture and 81.4% at 85% capture. Faster decomposition makes early well installation especially valuable because gas released before collection begins is lost. A two-year delay undermined returns, making electricity sales alone insufficient in the conservative collection scenarios.

Electricity Prices and Carbon Rules Shape the Returns

The base design adds generators in 2-megawatt modules as gas becomes available, eventually reaching 12 megawatts. Building gradually improves net present value, the estimated financial surplus after accounting for the timing of costs and income, by $6.7 million compared with installing everything upfront. Total capital spending reaches $21.6 million, with $9.9 million required at the start.

Assuming electricity sales at $0.075 per kilowatt-hour, construction costs of $1.8 million per megawatt, annual operating costs equal to 6% of installed capital and a 10% discount rate, net present value reached $15.7 million with full carbon crediting. Regional gas parameters lowered that value to $7.6–12.7 million. The internal rate of return was 20.2%, with simple payback in seven years and discounted payback in ten. The modeled electricity cost was $0.065 per kilowatt-hour, rising to $0.071 after selected overhaul, equipment electricity use and decommissioning allowances.

Without carbon credits, net present value fell to $4.1 million and the return to 13%. That surplus disappeared below an electricity price of about $0.065 per kilowatt-hour or above construction costs of $2.08 million per megawatt. Network charges for delivering electricity to customers could erase it too. Across 10,000 uncertainty simulations per modeling variant, the project remained viable without credits in 61–79% of cases. Viability with full crediting held in 99–100% of those simulations.

At $7 per tonne of carbon dioxide equivalent, full crediting would generate $32.4 million in cumulative carbon revenue. If flaring is treated as the legally required baseline under Mexico's NOM-083 framework, crediting only the extra benefit from electricity generation cuts that figure to $2.3 million.

Gas Engines Can Fit Alongside Better Waste Management

Gas engines offered the strongest financial performance among engines, microturbines, gas turbines and fuel cells after allowing for practical unit sizes, partial loads and gas compression. Fuel cells delivered the largest emissions reduction, 84.9%, and a negative net present value of $7.9 million. Engines could match or outperform turbines environmentally when methane slip stayed below roughly 3.5–4%. Strict requirements for exhaust controls and advanced gas cleaning could change the financial ranking.

Diverting 30% of the incoming waste mass as separated organics reduced landfill electricity output to about 630,000 megawatt-hours and required only 6 megawatts of capacity. The smaller gas project remained viable under the tested assumptions. Including treatment of the diverted material raised total emissions reductions to 76.8–83.9% with composting and 81.6–87.5% with anaerobic digestion, which produces biogas in controlled conditions.

The quantified gains relate to renewable energy and climate action, Sustainable Development Goals 7 and 13. These are planning estimates, with no measurements from an operating project, and the financial analysis excludes taxes and several site-specific costs. Waste surveys, gas pumping and quality tests, supplier quotations, an electricity purchase agreement and permitting studies are needed before investment.

Gas impurities can damage equipment, and engines release local air pollutants; health, employment and water benefits were not measured. Under the base model, 44.5% of eventual methane production occurs after 2044, making continued gas control essential after the study period ends.