Source: National Research Council of Science & Technology – Chemical Engineering Journal |
Author: Qahwa World |
Date: June 21, 2026

Just 90 Seconds Turns Wet Coffee Grounds into High-Grade Solid Fuel

Key Takeaways:

Korean researchers develop Flame Plasma Pyrolysis (FPP) technology to convert wet coffee grounds into biochar in just 90 seconds.
The technology eliminates the need for pre-drying, the biggest barrier to coffee waste recycling.
The resulting biochar achieves a heating value of 29.0 MJ/kg, comparable to high-grade anthracite coal.
The process achieves 83.3% mass reduction and triples fixed carbon content (from 15.6% to 46.2%).
The technology is 40 to 240 times faster than conventional hydrothermal carbonization.
Potential applications include food waste, sewage sludge, and agricultural residues with high moisture content.

Every year, global coffee consumption generates more than 10 million tons of spent coffee grounds, most of which end up landfilled or incinerated, releasing greenhouse gases and polluting the environment. While these grounds hold real energy potential, their high moisture content has long been a barrier to converting them into fuel or carbon products.

Now, a research team from the Korea Institute of Geoscience and Mineral Resources (KIGAM) has developed a revolutionary technology called Flame Plasma Pyrolysis (FPP), which directly treats biomass containing approximately 55% moisture without any pre-drying, converting it into high-quality biochar in just 90 seconds.

A Solution to the Growing Waste Challenge: From Waste to Energy

The global coffee industry faces a growing environmental challenge: more than 10 million tons of spent coffee grounds are produced annually, with most ending up in landfills or incinerators. These grounds are not just waste – they are wasted energy. Coffee grounds contain a heating value of up to 21.8 MJ/kg, but their high moisture content (approximately 55%) has been the biggest obstacle to economic utilization.

Flame Plasma Pyrolysis: A Revolution in Wet Waste Processing

The flame plasma system generates plasma flames at temperatures of approximately 800–900°C through the combustion of liquefied petroleum gas (LPG) and compressed air. Unlike conventional pyrolysis technologies, the process eliminates the need for any pre-drying treatment. During processing, the intense thermal energy rapidly vaporizes moisture trapped inside the biomass particles. The resulting pressure buildup triggers microscopic explosions known as the “popcorn effect,” which simultaneously enhance carbonization and create highly porous structures. Rather than acting as a barrier, moisture itself becomes a steam-activation agent that accelerates reactions and improves product quality.

Anthracite-Level Fuel Performance and Significant Quality Improvements

Under optimized conditions, the researchers achieved complete conversion within 90 seconds, with a mass reduction of 83.3%. The resulting biochar exhibited a heating value of 29.0 MJ/kg, approximately 33% higher than the original coffee grounds (21.8 MJ/kg) and comparable to that of anthracite coal.

Indicator	Before Treatment	After Treatment	Improvement
Heating Value (MJ/kg)	21.8	29.0	+33%
Fixed Carbon Content (%)	15.6	46.2	≈3×
Specific Surface Area (m²/g)	1.5	115.4	×77
Sulfur Compounds	Present	Fully Removed	No SOx Emissions

Dramatically Faster Than Existing Technologies

The new process offers substantial advantages in both processing speed and energy efficiency. Compared with hydrothermal carbonization (HTC), which typically requires one to six hours, the FPP process is 40 to 240 times faster. It also reduces treatment time by more than 20-fold compared with torrefaction, which generally requires at least 30 minutes. Because the system relies on combustion-generated plasma rather than electricity-intensive plasma devices, it lowers overall energy consumption while maintaining high processing performance.

Future Applications: From Coffee Waste to Decentralized Energy Systems

Beyond coffee waste, the technology is potentially applicable to a wide range of high-moisture organic wastes, including food waste, sewage sludge, and agricultural residues. Its compact process design and ultra-fast treatment capability make it particularly attractive for decentralized on-site waste-to-energy facilities, where transportation and drying costs often limit resource recovery efforts.

Researchers: “We Are Changing the Paradigm from Waste as a Problem to Waste as an Energy Resource”

Dr. Taejun Park, lead author of the study, said: “This technology presents a new paradigm in which waste is no longer viewed as a disposal problem but as a valuable energy resource.” He added: “We plan to expand the technology to various types of high-moisture organic waste and further optimize the process for industrial-scale commercialization.”

Research Context: Published in the Leading Chemical Engineering Journal

The research was published in the Chemical Engineering Journal (Elsevier, Impact Factor 13.2), a leading international journal in chemical engineering. The study demonstrates a new approach for transforming wet organic waste into valuable energy resources while advancing carbon-neutral waste management strategies. The Korea Institute of Geoscience and Mineral Resources (KIGAM) is a government-funded research institute specializing in geoscience, mineral resources, energy technologies, and Earth system science.

Frequently Asked Questions About Coffee Waste-to-Fuel Technology

Q: What is Flame Plasma Pyrolysis technology?

A: A revolutionary technology developed by Korean researchers that converts wet biomass (such as coffee grounds) into high-quality biochar in just 90 seconds, without any pre-drying.

Q: What is the heating value of the resulting biochar?

A: 29.0 MJ/kg, which is 33% higher than the original coffee grounds and comparable to high-grade anthracite coal.

Q: How long does the conversion process take?

A: Just 90 seconds – 40 to 240 times faster than conventional hydrothermal carbonization techniques.

Q: Can this technology be applied to other types of waste?

A: Yes, it can be applied to food waste, sewage sludge, and agricultural residues with high moisture content.

Q: What are the environmental benefits of this technology?

A: It reduces waste sent to landfills, lowers greenhouse gas emissions, and produces clean sulfur-free fuel, preventing SOx emissions.

Flame Plasma Pyrolysis technology represents a paradigm shift in converting wet organic waste into valuable energy resources. With rapid, cost-effective processing, this technology opens new horizons for sustainable waste management and renewable energy production. As global coffee consumption continues to grow, this technology may be the key to turning one of the biggest waste challenges into an energy and environmental opportunity.

Prepared and edited by: Qahwa World – Based on a study published in the Chemical Engineering Journal (Elsevier) by the Korea Institute of Geoscience and Mineral Resources.

Publication date: June 21, 2026

Dubai – Qahwa World

Using leftover brewed coffee or spent coffee grounds has long been a familiar practice among gardeners looking for simple, sustainable ways to improve their soil. Research from institutions including Oregon State University, Washington State University, and the University of Missouri, along with findings from peer-reviewed studies published in recent years, indicates that coffee residues can benefit plants—mainly when used as part of compost or as a soil amendment. Experts, however, stress that coffee grounds should not be considered a complete fertilizer.

Coffee Grounds Provide Several Plant Nutrients

Spent coffee grounds contain a number of nutrients useful for plant growth, though generally in modest quantities.

Nitrogen is the most significant component, typically accounting for about one to two percent of the grounds by weight. Most of this nitrogen is organic and bound in proteins, which means it becomes available slowly as soil microbes break down the material. Nitrogen plays an essential role in plant development, supporting protein formation and leafy growth.

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Coffee grounds also contain potassium, which helps regulate water balance, supports photosynthesis, and assists with nutrient movement within plants. Smaller amounts of magnesium and copper are present as well, along with trace minerals such as iron, manganese, zinc, boron, and calcium. Magnesium is particularly important because it is a central component of chlorophyll, the pigment that allows plants to convert sunlight into energy.

Minor amounts of phosphorus and calcium are also found in the grounds.

By contrast, the liquid left after brewing coffee contains much smaller nutrient concentrations because most solids remain in the grounds. Laboratory analyses conducted through 2025 indicate that the overall nutrient profile of coffee grounds has remained consistent, although compost mixtures that include coffee residues can show higher total nitrogen levels.

Soil Microbes Are the Real Beneficiaries

Researchers note that the primary benefit of coffee grounds in gardening comes from how they affect soil biology.

The organic carbon in coffee grounds provides an energy source for soil microorganisms. As these microbes break down the material, they produce humus-like substances that improve soil health. These changes can lead to better soil structure, improved water retention, and enhanced drainage.

Microbial activity can also make certain nutrients—such as phosphorus, iron, and zinc—more accessible to plants, particularly in alkaline soils. In addition, organic matter produced during decomposition may help bind certain chemicals and heavy metals in soil, reducing the risk of runoff.

Read also: Center for Circular Economy in Coffee Launches Global Survey on Spent Coffee Grounds Valorization

Recent studies continue to explore these effects. A 2025 experiment involving sunflower plants found that composted coffee grounds incorporated into soil mixtures improved germination rates and plant growth compared with untreated soil. Another trial conducted in the United Arab Emirates in 2024 reported improved radish growth and soil quality when recycled coffee-ground fertilizer was used.

A Possible Tool Against Slugs

Coffee may also play a limited role in pest control.

Experiments suggest that solutions containing caffeine can repel or kill slugs and snails. In laboratory tests, strong brewed coffee solutions caused these pests to leave treated areas and eventually die due to the toxic effects of caffeine.

Some gardeners also report reduced slug activity when coffee grounds are used as a surface dressing or mulch. However, researchers say evidence remains limited, and there is little scientific support for claims that coffee grounds repel cats, eliminate weeds, or control plant diseases in gardens.

Risks of Using Too Much Coffee in Soil

Despite its potential advantages, coffee residues can create problems if used improperly.

One of the most common misconceptions is that coffee grounds act as a complete fertilizer. In reality, they contain relatively low levels of phosphorus and calcium, and the nitrogen they provide becomes available slowly. During decomposition, microbes may temporarily use nitrogen from the soil, which can reduce the amount available to plants.

Another misunderstanding involves soil acidity. Although brewed coffee is acidic, used coffee grounds are generally close to neutral in pH. Because of this, they usually do not significantly acidify soil.

Read also: New study: coffee grounds may be beneficial for brain health

When applied in thick layers, coffee grounds can also compact and form a dense surface crust. This barrier can restrict water infiltration and limit air movement into the soil, potentially harming plant roots.

Fresh grounds may also slow seed germination or inhibit early plant growth. Compounds such as caffeine and certain plant chemicals present in raw grounds can be harmful to seedlings when used in large quantities.

Finally, leftover coffee containing milk or sugar may attract pests or encourage unwanted microbial growth.

How Experts Recommend Using Coffee Grounds

Garden specialists generally recommend composting coffee grounds before adding them to soil.

A balanced compost mixture might include leaves, grass clippings, and coffee grounds, with the grounds making up no more than about one-fifth of the total volume. When regularly turned and properly maintained, the compost typically becomes usable within several months.

Coffee grounds can also be incorporated directly into soil in small amounts. Mixing a thin layer into the top few inches of soil is generally considered safe. When used as mulch, the layer should remain very thin and ideally be covered with coarser organic materials such as leaves or bark to prevent compaction.

Leftover brewed coffee can sometimes be used as a diluted watering solution after it has cooled, though gardeners typically dilute it with water to reduce its strength.

A Useful Resource—When Used Wisely

Research suggests that coffee grounds can contribute to healthier soil when used carefully. They add organic matter, support microbial life, and may provide limited pest-repelling effects. At the same time, experts caution that excessive use can cause more problems than benefits.

For gardeners, the best approach is to treat coffee grounds as a supplementary soil amendment rather than a primary fertiliser—ideally as part of compost and combined with other proven soil-improvement practices.

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