Biochar boosts hydrogen and methane yield in next-generation food-waste-to-energy systems

Maximum Academic Press

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By integrating biochar into semi-continuous reactors operating for 100 days, the research shows notable gains in gas yield, stronger resistance to acidification, and more resilient microbial communities.

Food waste continues to rise worldwide, placing pressure on waste-management infrastructure and increasing greenhouse gas emissions. Anaerobic digestion (AD) is widely used to convert organic waste into biogas, yet conventional one-phase digesters often struggle with poor stability, high CO₂ content, and sensitivity to microbial shifts. TPAD—which separates hydrogen and methane production—provides improved efficiency but remains limited by acid build-up and low tolerance for high organic loading rates. Chemical buffers can stabilise pH but add cost and may disrupt microbial activity. Given these challenges, exploring sustainable additives such as biochar is essential to improving TPAD performance and enabling wider industrial adoption.

A study (DOI:10.48130/een-0025-0010) published in Energy & Environment Nexus on 21 October 2025 by Yusron Sugiarto’s team, The University of Western Australia, highlights how biochar enables TPAD systems to operate at loading levels previously associated with failure, offering a practical strategy to enhance renewable gas recovery from food waste.

The study evaluated the role of biochar in a TPAD system treating food waste by operating paired semi-continuous stirred-tank reactors—with and without biochar—over 100 days across seven stages of increasing organic loading rates (0.5–6.0 g VS/(L·d)). In both the hydrogen-producing first reactor (R1) and the methane-producing second reactor (R2), the team monitored gas production rates (H₂ and CH₄), pH dynamics, volatile fatty acid (VFA) profiles, and microbial community composition to link process performance with underlying biochemical and microbial mechanisms. In R1, hydrogen production started on day 2 and increased as loading and dilution rates were adjusted, but reactors amended with biochar consistently showed higher H₂ production, with gains of 45–88% over controls and no decline even at the highest loading of 6.0 g VS/(L·d). These improvements were associated with more stable pH (≈5.5 versus 4.5–5.0 in controls) and moderated VFA accumulation, particularly reduced propionic acid build-up at high loadings. In R2, biochar likewise enhanced methane production: CH₄ appeared earlier, CH₄ content increased, and the CH₄ production rate remained stable at ~1,900 mL/d, whereas controls declined by ~12% at the highest loading as pH fell and VFAs accumulated. Throughout both phases, biochar-treated reactors maintained higher pH (around 5.5 in R1 and 7.2–7.3 in R2) and lower inhibitory VFA levels, confirming its buffering and metabolic support functions. Microbial analyses showed that biochar substantially enriched Clostridiaceae in both phases and promoted the growth of key methanogenic archaea, especially Methanosarcinaceae and Methanobacteriaceae, fostering stronger syntrophic networks and facilitating direct interspecies electron transfer. Together, these method–result linkages demonstrate that biochar stabilises semi-continuous TPAD and enables sustained hydrogen and methane production under loading conditions that destabilise conventional systems.

The findings demonstrate that biochar is a practical and cost-effective additive for stabilising TPAD systems treating food waste. By preventing acidification, enhancing microbial resilience, and enabling high-rate digestion at OLRs up to 6.0 g VS/(L·d), biochar allows TPAD systems to match or exceed the throughput of conventional anaerobic digesters while producing a higher-quality renewable gas mixture. Municipal waste facilities, agricultural biogas plants, and decentralised food-waste-to-energy systems could adopt this approach to increase renewable energy recovery, lower reliance on chemical buffers, and improve operating reliability. The study also provides a microbial basis for designing future biochar-enhanced digestion technologies.

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References

DOI

10.48130/een-0025-0010

Original Source URL

https://doi.org/10.48130/een-0025-0010

Funding information

This research received partial financial support from the Australian Research Council through the ARC Linkage Projects scheme (ARC LP100200137), the ARC Discovery Projects scheme (DP210103766 and DP220100116), and the Future Energy Export CRC (FEnEX CRC Project # 21.RP2.0059). Y Sugiarto expresses gratitude to the Directorate of Research and Community Service at Universitas Brawijaya, the EQUITY Program (Project No. 4559/2023), and the Woodman Point Wastewater Treatment Plant for supplying wastewater sludge.

About Energy & Environment Nexus

Energy & Environment Nexus is a multidisciplinary journal for communicating advances in the science, technology and engineering of energy, environment and their Nexus.

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DOI

10.48130/een-0025-0010 

Method of Research

Experimental study

Subject of Research

Not applicable

Article Title

Enhancing H2 and CH4 production with biochar addition in two-phase anaerobic digestion of food waste

 

New critically endangered ‘fairy lantern’ species discovered in Malaysia

Pensoft Publishers

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video: 

Thismia selangorensis in its habitat.

view more 

Credit: Gim Siew Tan

Researchers in Malaysia have discovered a new endemic ‘fairy lantern’ plant species with fewer than 20 individuals known to exist in the wild. They have classified the species as Critically Endangered under IUCN Red List criteria.

Described in the open-access journal PhytoKeys, the peach-to-pink Thismia selangorensis joins the expanding Thismia genus, which includes 120 known species of mycoheterotrophic plants. Unlike familiar phytosynthetic plants, mycoheterotrophic species lack chlorophyll and do not get their energy from the sun. Instead, they depend solely on a parasitic relationship with fungi in the soil for their nutrition.

Species from this genus are typically found in undisturbed forests rich in leaf litter, where moist and shaded soils allow them to remain hidden for much of their lives, making their discovery extremely difficult. Thismia selangorensis was no exception. Standing at only around 10 cm tall,  with coral‑like roots and a  peach-to-pink flower that develops into a distinctive umbrella‑shaped “mitre” topped by three slender club‑shaped appendages, Thismia selangorensis had gone unnoticed despite decades of human activity in its habitat. Among the earlier individuals found, one was located in a hole at the base of a tree, as if living in a cave. Later, a few more individuals were found in more open areas near tree buttresses along the riverbanks.

“This discovery shows that significant scientific finds are not limited to remote jungles; they can also be made in ordinary environments where constant human activity leaves little room for expectation. Protecting Thismia selangorensis will require cooperation among researchers, the forest department, stakeholders, and the public, as its survival depends on how carefully we tread in its habitat.,” said Siti-Munirah Mat Yunoh (FRIM), lead author of the research paper, “The most important effort now is to raise awareness about this species so the public realises that it exists – right here, in this small corner of the world, and nowhere else, at least for now. Understanding its presence is the first step towards ensuring that this extraordinary plant is not lost before many people even know it exists.”.

Naturalist Tan Gim Siew first spotted  the elusive species in November 2023 during a routine photography visit to Taman Eko Rimba Sungai Chongkak, part of the Hulu Langat Forest Reserve and a long‑established picnic and camping destination near Kuala Lumpur. A tiny plant was growing among moist leaf litter near the buttress roots of a riverside tree. Follow-up surveys revealed that fewer than 20 individuals were present, with an estimated occupied habitat of only four km².

The authors highlight that, although part of the Sungai Chongkak forest remains relatively intact, plants growing close to riverside campsites and picnic areas could easily be destroyed unintentionally by trampling or flooding. They recommend careful management of visitor access around known sites, continued monitoring of the population and further botanical surveys to clarify whether the species occurs beyond its currently known locality.

Original source

Siti-Munirah MY, Gim Siew T, Mat-Tahir MF, Azhar A (2025) Thismia selangorensis (Thismiaceae): a new mitriform fairy lantern species from Selangor, Malaysia. PhytoKeys 267: 9-21. https://doi.org/10.3897/phytokeys.267.157968

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Journal

PhytoKeys

DOI

10.3897/phytokeys.267.157968 

Article Title

Thismia selangorensis (Thismiaceae): a new mitriform fairy lantern species from Selangor, Malaysia

Article Publication Date

28-Nov-2025

  

Thismia selangorensis

Credit

Gim Siew Tan

Thismia selangorensis

Thismia selangorensis

Thismia selangorensis

Researchers with Thismia selangorensis.

Credit

Gim Siew Tan

Thismia selangorensis. A. A plant with full flower and coralliform roots; A1. Claviform tip of mitre appendage; B. Outer tepal and filaments; C. Inner tepal forming a mitre; D. Floral tube and mitre; E. Mitre viewed from above; F. Floral tube with ovary and flower bud surrounded by bracts and tepals split on apex; G. Longitudinal section of floral tube, showing inner part (H); H. Inner surface of floral tube; I. Top view of stamens; J. Inner view of a stamen; K. Outer view of a stamen; L. Six stamens viewed from below; M. Stigma. 

Credit

Siti-Munirah MY and Mohd Faizal

 IPA LAGER

Technology boosts hop production in Brazil and paves the way for new bioproducts

Project developed in the state of São Paulo, Brazil, allows for the highly efficient extraction of aromatic and bioactive compounds, reducing logistics costs and increasing beer quality

Fundação de Amparo à Pesquisa do Estado de São Paulo

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image: Ingredient is responsible for the aroma and flavor of beer view more 

Credit: Levi Pompermayer Machado/UNESP)

Despite being the third-largest producer and consumer of beer worldwide, Brazil depends almost entirely on hop imports. Less than 1% of the ingredient responsible for the bitterness, aroma, and flavor of beer is grown locally. However, a new project involving Brazilian scientists and producers in the Vale do Ribeira region of the state of São Paulo seeks to change this scenario. The project aims to make domestic hop production more efficient and viable while boosting the development of new bioproducts.

The project was born within the Center for Research on Biodiversity Dynamics and Climate Change (CBioClima), one of the Research, Innovation, and Dissemination Centers (RIDCs) supported by FAPESP and based at São Paulo State University (UNESP). The project is investing in supercritical extraction with carbon dioxide (CO₂), a technology that is already well-established in countries such as Germany and the United States. This method efficiently extracts aromatic and bioactive compounds from hops, reducing logistics costs and improving beer quality.

“Brazilian hops are normally sold in pellets [dehydrated and pressed flowers] to breweries. However, with this technology, hops can be marketed in oil form, which, in addition to logistical gains, yields beer production results that are far superior to conventional methods,” explains Levi Pompermayer Machado, a professor at UNESP and one of the researchers involved in the project.

In addition to CBioClima, the project includes the National Institute of Science and Technology in Nanotechnology for Sustainable Agriculture (INCT NanoAgro), the Aquário de Ideias incubator, with startups from Vale do Ribeira, as well as Bioativos Naturais and Kalamazoo – two companies supported by FAPESP’s Innovative Research in Small Businesses Program (PIPE). The producers are part of the SP Produz 2025 program, run by the São Paulo state government, which offers strategic support to strengthen local production chains.

In the study published in the journal Biomass Conversion and Biorefinery, the researchers compared the extraction of hops at Atlântica Hops in the municipality of Juquiá in Vale do Ribeira using conventional and supercritical CO₂ methods. While traditional extraction, which uses organic solvents or a technique known as steam stripping, yields about 15% extract with 9% α-acids (the compounds responsible for the bitterness of beer), the CO₂ method achieves up to 72% α-acids. Additionally, the process results in a lower volume, better preservation, and an increase of up to 20% in beer productivity.

“Each hop has a unique flavor, which is defined by what we call terroir, and that’s what the industry is looking for. In the study, we also conducted analyses of the sensory profile of the hop extract in pellets and the extract we produced. There was a slight change in flavor, but the sensory signature of the product remained more or less the same. Therefore, with all this improvement in efficiency and quality, the characteristics of the terroir are almost entirely maintained,” he says.

Machado points out that the technology tested in Vale do Ribeira stands out for adhering to the principles of green chemistry. Traditional methods use large amounts of water or petroleum-based solvents to separate essential oils from hops.

Supercritical extraction, on the other hand, uses carbon dioxide under high-pressure, high-temperature conditions where it exists in a state between liquid and gas (the supercritical state). In this state, CO₂ acts as a natural solvent, penetrating deeply into the raw material and extracting its compounds with high efficiency.

“In addition, the CO₂ used in supercritical technology is recaptured at the end of the process, which avoids atmospheric emissions and eliminates chemical residues in the extract. This makes the method more efficient and environmentally responsible,” says Machado.

The researcher states that the main objective of the project is to provide producers with cultivation options that have a smaller environmental footprint and greater added value (as is the case with hops), rather than expanding agricultural frontiers with low-value commodities such as soybeans and sugarcane.

“We’re talking about producing more in a much smaller cultivated area, with a crop that responds well to climate change and offers multiple market possibilities,” the researcher points out.

Circular economy

Another advantage of this technology is that the resulting extracts can be used not only in the brewing industry but also in the cosmetics and pharmaceutical sectors. In addition to the extracts, the researchers analyzed the waste left over after extraction (spent hops).

Johana Marcela Concha Obando, a postdoctoral fellow at INCT NanoAgro at UNESP who is involved in the project, explains that hop waste still contains bioactive compounds with high antioxidant potential, such as phenolics and flavonoids. “Since the technique doesn’t use reagents, this waste isn’t lost in the process and can be used for other purposes,” she explains.

The study’s biochemical analysis revealed that, even after removing the main active ingredients, the residual biomass retains properties that can be used in new products. “With the extract, we’re no longer serving just the brewing niche, but reaching five, six, or even ten different sectors,” Machado celebrates.

About São Paulo Research Foundation (FAPESP)
The São Paulo Research Foundation (FAPESP) is a public institution with the mission of supporting scientific research in all fields of knowledge by awarding scholarships, fellowships and grants to investigators linked with higher education and research institutions in the State of São Paulo, Brazil. FAPESP is aware that the very best research can only be done by working with the best researchers internationally. Therefore, it has established partnerships with funding agencies, higher education, private companies, and research organizations in other countries known for the quality of their research and has been encouraging scientists funded by its grants to further develop their international collaboration. You can learn more about FAPESP at www.fapesp.br/en and visit FAPESP news agency at www.agencia.fapesp.br/en to keep updated with the latest scientific breakthroughs FAPESP helps achieve through its many programs, awards and research centers. You may also subscribe to FAPESP news agency at http://agencia.fapesp.br/subscribe.

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Journal

Biomass Conversion and Biorefinery

DOI

10.1007/s13399-025-06903-z 

Article Title

Chemical and biotechnological characterization of supercritical CO2 extracts and residual Humulus lupulus biomass from the Brazilian Atlantic Forest