Bolivian Farmer Turns Waste Into Tractor Fuel at Half Diesel’s Cost

Inside Etson Machaca’s small plant in Bolivia’s Altiplano, oxygen-limited heat breaks down plastic bags, tires, used oil and other discarded materials. Some of the resulting hydrocarbon vapor is cooled into a diesel-like liquid, which Machaca reportedly uses in his tractors and other agricultural equipment.

The process, known as pyrolysis, is giving his farm an unusually direct response to high fuel costs. Machaca’s fuel reportedly costs between $2.27 and $3.25 per U.S. gallon to produce, compared with approximately $5.83 per gallon for conventional diesel in Bolivia. He uses the output on his own farm rather than selling it, and the figures have not been independently verified.

How waste becomes a liquid fuel

Pyrolysis is different from ordinary combustion. Instead of burning material with a supply of oxygen, the reactor heats hydrocarbon-rich waste with little or no oxygen. Long molecular chains then break into smaller compounds, producing gases, solid residue and vapors that can be condensed into oil.

The basic chemistry is established, but output varies significantly with the feedstock and operating conditions. Plastic type, contamination, temperature, heating rate, reactor design and residence time can all change how much liquid emerges and what that liquid contains. The account of Machaca’s operation cites an experimental yield of roughly three-quarters of the input mass as usable fuel, but it provides no plant test records to confirm his actual yield.

This variability becomes particularly important when a reactor accepts mixed material. Tires, used oil and different plastics do not produce one uniform chemical stream. Additives, labels, residue and chlorine-containing plastics can alter the oil, gas and solid by-products. Government technical guidance also notes that pyrolysis off-gases require treatment before release, even though the process operates without ordinary combustion.

Diesel-like properties are only a starting point

Machaca’s oil reportedly has density and viscosity characteristics resembling diesel. Those properties affect pumping, injection and atomization, but they cannot establish whether the fuel consistently meets a recognized diesel specification.

Other characteristics can be equally consequential: ignition quality, heating value, flash point, sulfur, acidity, water, ash, contaminants and distillation behavior. Variation in those properties may affect cold starting, combustion timing, injector deposits, lubrication, corrosion and exhaust emissions. No fuel-standard analysis, emissions measurements or long-term durability results have been provided for Machaca’s product.

Controlled research illustrates the gap between making an engine run and validating a fuel for sustained service. A 2024 experimental study of plastic pyrolysis oil tested blends containing up to 15% waste-derived oil in conventional diesel in an unmodified single-cylinder engine. The researchers reported broadly comparable performance and emissions for those low-level blends, but results varied by blend and engine speed. The work did not test Machaca’s mixed-feedstock fuel or establish that an unblended farm product would behave the same way.

Other studies summarized in that research have produced conflicting emissions and efficiency findings. Differences in raw material, post-treatment and fuel composition make broad comparisons difficult. A tractor operating successfully today therefore supplies useful field experience, but not a substitute for controlled analysis of injector condition, lubricant contamination, deposits, exhaust output and wear over many operating hours.

The price advantage has a national context

The reported savings arrive as Bolivia changes how diesel is priced. The country imports roughly 90% of its diesel, and the government recently ended state subsidies in favor of prices that track international benchmarks, according to Reuters’ account of the policy change. For a mechanized farm exposed to fuel shortages and import costs, producing liquid fuel from nearby waste can reduce dependence on the retail supply chain.

That advantage remains specific to Machaca’s small operation. Its reported cost does not include enough detail to compare energy consumption, labor, feedstock preparation, reactor maintenance, emissions controls or residue management with commercial diesel on a consistent basis. Nor does one farm establish that enough suitable waste could be collected and processed economically at larger scale.

Machaca has demonstrated the most immediate requirement: his plant can create a combustible liquid that reportedly powers his agricultural machinery for about half the local diesel price. The next engineering milestone is more demanding repeatable fuel testing and tracked engine inspections that show whether those savings survive years of injector service, emissions control and mechanical wear.

By Thomas Caldwell — AMI’s senior editor for mechanical and mobility engineering, covering vehicle electronics, systems integration, electrification, chassis systems, propulsion, and safety policy.