Granulation and pyrolysis of agricultural residues for an enhanced circular economy

• Low-temperature pyrolysis converts agricultural biomass into biochar, animal feed and briquettes. • Barley straw pellets showed the best strength and highest pyrolysis yield. • Optimized granulation process produced robust pellets with 85 % biomass and 15 % peat. • Lettuce cultivation tests showed peat-barley straw pellets yielded the best plant growth results. This study highlights a sustainable approach to agricultural waste management by transforming residues into value-added products through granulation and pyrolysis. Agricultural biomass, a prevalent waste stream, holds great potential as a key ingredient for enhancing soil health. However, the common practice of incineration diminishes this opportunity by wasting valuable resources. This investigation sought to demonstrate that low-temperature slow pyrolysis of biomass can be used to create value-added products such as animal feed, biochar, and heating briquettes. The study involved a comparative analysis of wheat straw, barley straw, and oat husk for biochar production, examining key properties like moisture content, ash content, and fiber composition. The optimal granulation process for combining these materials with peat was established, resulting in robust pellets consisting of 85 % biomass and 15 % peat. Pyrolysis was conducted at 500 °C with a heating rate of 5 °C per minute. The resulting granules were evaluated for their strength, density, and moisture absorption. The barley straw pellets were found to have the best mechanical strength of 89.40 N, the best moisture absorption capacity of 49.50 % and the highest product yield of 54.1 % after pyrolysis. When used in lettuce cultivation, the combination of peat with barley straw as a binder yielded the most promising results. Introducing circularity in biomass reduces waste, enhances soil health and creates economic opportunities, reinforcing the principles of a circular economy. This approach promotes resource efficiency, minimizes environmental impact and contributes to a more sustainable agricultural sector.