Two Clever Chemical Tricks Turn Farm Waste Gas Into a Diesel Rival at 1 Euro a Kilo

Every year, farms, landfills and wastewater plants belch out millions of tonnes of biogas, a methane-rich mixture that is often flared or vented after the energy-rich methane has been extracted. Now a team of chemical engineers in the Netherlands and Spain has shown that this humble waste stream can be transformed into a clean-burning diesel alternative at a cost of roughly one euro per kilogram, using a pair of intensified chemical processes that sidestep some of the most stubborn thermodynamic limits in industrial chemistry. The study, published in Frontiers in Chemical Engineering, is the first to integrate sorption-enhanced steam reforming of biogas with sorption-enhanced dimethyl ether synthesis in a single plant, and the numbers suggest the combination is both technically and economically compelling.

Dimethyl ether, or DME, is something of an unsung hero in the sustainable fuels world. It is non-toxic, produces low combustion emissions, and can be handled much like conventional liquefied petroleum gas, making it a promising substitute for diesel in compression ignition engines. It can also serve as a hydrogen carrier, storing and transporting clean energy in liquid form. The catch has always been cost: producing DME from biogas requires first converting methane into syngas, then synthesising methanol, and finally dehydrating it to DME, a multi-step chain in which each stage loses energy and adds expense. Previous techno-economic studies of bio-DME plants have reported break-even selling prices as high as 1900 to 5000 euros per tonne, far above what the market would bear.

The new research, led by A. Capa of TNO in the Netherlands and the Spanish National Research Council, together with colleagues including J. Boon of TNO, attacks this problem at both ends of the production chain simultaneously. At the front end, the team employs sorption-enhanced steam reforming, or SESR, a process in which methane steam reforming and the water-gas shift reaction are combined with in situ carbon dioxide capture in a single reactor bed containing both a nickel-based reforming catalyst and a calcium oxide-based sorbent. By removing CO2 as soon as it forms, the process overcomes the equilibrium limitations that normally cap hydrogen productivity, yielding a high-purity hydrogen stream at 675 degrees Celsius and 5 bar.

At the back end, the plant uses sorption-enhanced DME synthesis, known as SEDMES, a novel single-step route in which the water produced during methanol synthesis and dehydration is removed in situ using a zeolite adsorbent. Following Le Chatelier’s principle, continuously stripping water from the reaction mixture pushes the equilibrium towards DME formation, improving both carbon and hydrogen conversion. The concept has already been demonstrated in a multi-column test rig at TNO, achieving carbon yields up to 95 percent in a single step when operating with pure CO2 and renewable hydrogen. The new study is the first to feed this intensified synthesis unit directly with the hydrogen and CO2 streams generated by an intensified reforming unit.

The team built a full process simulation in Aspen Plus, integrating a 40 MW SESR unit with a SEDMES system operating at 250 degrees Celsius and 50 bar. In the base-case configuration, without any integration synergies, the plant consumed roughly 7 tonnes per hour of biogas as feedstock and produced 4.4 tonnes per hour of bio-DME, but required an additional 4.2 tonnes per hour of biogas as fuel to regenerate the calcium oxide sorbent through calcination at 900 degrees Celsius. The cold gas efficiency stood at 64 percent, the global DME yield at 39 percent, and the net efficiency, once external utilities were accounted for, dropped to just 47 percent.

From there, the researchers systematically explored three integration strategies to squeeze more value from the same biogas. The first was heat integration: a significant portion of the cooling demand in the base case, roughly 62 percent, arose from the temperature mismatch between the reforming section, where streams exit at 675 and 900 degrees Celsius, and the DME synthesis unit, which operates at 250 degrees. By replacing coolers with heat exchangers that generate steam for the SESR unit, following pinch analysis principles, the team integrated 3.5 MW of cooling duty, raising the cold gas efficiency by about 3 percentage points.

The second strategy recycled the unconverted gases leaving the SEDMES unit, which are rich in hydrogen, as fuel in the external burner that supplies heat to the SESR calciner. This reduced biogas consumption as fuel by roughly 4 percentage points, lifting the cold gas efficiency to 71.3 percent and the global DME yield to 43.5 percent. The third and most impactful synergy was steam integration: during SEDMES adsorbent regeneration, water is desorbed at 250 degrees Celsius, producing low-pressure steam that can partially meet the SESR unit’s steam demand. When biogas is used as the purge gas for desorption, the steam and purge gas can be recycled directly to the reformer without condensation, avoiding the energy penalty of latent heat. The result: a cold gas efficiency of 74.1 percent and a global DME yield of 45.3 percent, with water consumption reduced by about 38 percent.

On the economic side, the levelised cost of DME for the fully integrated plant is estimated at approximately 1 euro per kilogram, notably lower than the 1.3 euros per kilogram reported for alternative power-to-X DME routes that rely on electrolytic hydrogen and captured CO2. Biogas cost dominates the operating expenses, accounting for roughly 49 percent, while hydrogen production equipment represents the largest share of capital investment at 38 percent. A sensitivity analysis showed the levelised cost varies between 0.8 and 1.25 euros per kilogram across plus or minus 50 percent variations of key parameters, with biogas price exerting the largest influence. Net present value analysis indicates the plant becomes profitable when DME sells above roughly 1000 euros per tonne, with payback times shrinking to about 5 years at 1500 euros per tonne, considerably less demanding than the break-even prices of 1900 to 5000 euros per tonne reported in earlier literature.

The carbon balance also improves with increasing integration, with nearly 54 percent of total carbon ending up as utilised carbon in the form of DME, driven mainly by reduced flue gas emissions from the external combustor. The remaining CO2 that cannot be converted due to stoichiometric constraints is sent to storage, meaning the plant operates as a carbon capture and utilisation system that avoids the emissions associated with conventional biogas upgrading. The authors note that an electrified calciner could eliminate the main flue gas stream entirely, and that carbon pricing mechanisms or incentives for biogas utilisation, already implemented in many EU countries, could further strengthen the economic case.

Challenges remain before this concept reaches commercial scale. The SEDMES process requires careful temperature control, as the reactor must simultaneously accommodate the exothermic nature of DME synthesis and water adsorption, and inadequate heat removal could reduce performance and accelerate catalyst deactivation. The long-term performance of catalysts, sorbents and adsorbents under continuous cycling is another open question, as is the overall process complexity. Yet the study demonstrates that intensifying both hydrogen production and DME synthesis enables an efficient, economically attractive pathway for bio-DME from biogas, offering opportunities for decentralised, carbon-efficient fuel production that could contribute to future renewable fuel and chemical value chains. As the energy transition accelerates, turning farm waste into a diesel rival at one euro a kilogram may prove one of the more elegant tricks in the sustainable chemistry playbook.

Subject of Research: Integrated process design for sorption-enhanced steam reforming of biogas and sorption-enhanced DME synthesis: a techno-economic study

Article Title: Integrated process design for sorption-enhanced steam reforming of biogas and sorption-enhanced DME synthesis: a techno-economic study

Article References: Capa, A., Tyraskis, I., Skorikova, G., Rubiera, F., Pevida, C., Gil, M. V., & Boon, J. (2026). Integrated process design for sorption-enhanced steam reforming of biogas and sorption-enhanced DME synthesis: a techno-economic study. Frontiers in Chemical Engineering, 8, Article 1915733. https://doi.org/10.3389/fceng.2026.1915733

Image Credits: AI Generated

DOI: 10.3389/fceng.2026.1915733

Keywords: Integrated, process, design, sorption-enhanced, steam, reforming, biogas, synthesis, techno-economic, scientific research