Biowaste conversion: A sustainable alternative to landfilling through coupled recovery of dried biomass and water

Landfilling raw biowaste causes serious problems in all countries that employ this method. While biowaste drying technology addresses this issue by focusing on the biomass component, it often neglects the potential for water recovery. This study presents an innovative device that combines a heat source with an ash biofilter to optimize the gravity-driven recovery of moisture from biowaste, including potato peels, orange peels, and coffee grounds. The device provides an effective solution for the simultaneous recovery of dried biomass and water from biowaste, thereby overcoming the limitations of conventional dehydration treatments and further reducing environmental impact. At temperatures of 55 °C and 70 °C for 24 h, 80% of the water was recovered. Dry biomass was obtained with a moisture content of ≤ 10%, achieving reduction rates ranging from 90.16% to 98.08% at 55 °C and from 92.11% to 98.24% at 70 °C, demonstrating greater efficiency than bio-drying reactors, with drying kinetics ranging between 0.948 and 0.995. Physicochemical analyses indicated that treatment at 55 °C preserved the nutrients in dried biomass more effectively than treatment at 70 °C. Specifically, the proportions of organic matter, total organic carbon, and total nitrogen content were higher at 55 °C than at 70 °C, in contrast to electrical conductivity. The results demonstrated that the device has the advantage of recovering water in free form over a short duration at a rate of 4.60% to 5.48%/h. The nutrient concentrations in the recovered water were significantly lower compared to devices lacking a biofilter, with a chemical oxygen demand of less than 471 mg/L for all three types of biowaste. This process could potentially be utilized in the future as a treatment following door-to-door collection of biowaste.