The rising demand for sustainable energy has sparked interest in biomass, particularly spent coffee grounds (SCGs), which are increasingly recognized as a renewable resource.

Valorizing SCGs through thermochemical processes like gasification provides a viable waste-to-energy conversion pathway.

The gas yields of carbon monoxide and methane varied significantly depending on the type of catalyst used and the temperature, highlighting the importance of optimizing conditions for effective biomass conversion.

Thermogravimetric analysis revealed that different catalysts significantly influenced the thermal decomposition behavior of SCGs, ultimately enhancing gasification efficiency.

This research contributes to sustainable waste management by valorizing SCGs and biochar, aligning with circular economy principles.

The necessity of using organic materials for soil improvement is underscored by the significant soil pollution challenges faced in China.

Results indicate that GWC application significantly enhances soil quality by reducing bulk density and increasing levels of organic matter, organic carbon, total nitrogen, available phosphorus, and available potassium.

For gasification experiments, spent coffee grounds were collected from local restaurants in Tokyo and dried, with tests conducted at temperatures of 800 °C, 900 °C, and 1000 °C.

Metal oxide catalysts, including nickel oxide, manganese oxide, aluminum oxide, and iron oxide, were selected for their catalytic properties to enhance the gasification process.

The study also investigates the impact of green waste compost (GWC) on soil nutrient conditions, aiming to reduce environmental pollution and improve soil productivity.

Among the catalysts tested, manganese exhibited the highest catalytic activity at 1000 °C, followed by iron, while aluminum and nickel were less effective.

Additionally, the production of bio-nutrients from SCGs and biochar through composting has shown positive effects on the growth of garden cress and spinach.