Large amounts of unutilized silage are available in agriculture as well as from municipalities harvesting meadows and grasslands.At the same time, biogas plants with crop-based substrates are looking for alternative substrates to adapt to EU RED and toincrease profitability. Unutilized silage that would not otherwise be used for feed can be an excellent biogas substrate, but thematerial is often coarse and pretreatment is necessary. This project was performed as a case study to substitute 20% of the cropbasedsubstrate used today (maize, whole-crop silage and grain) with unutilized silage bales for the Jordberga biogas plant inthe south of Sweden.

Three different mobile machines for disintegration of silage bales were used in practical trials to evaluate which was most effectiveat reducing particle length and damaging the structure of the grass for improved digestion. Two of the machines used ahammermill technique for disintegration and the third used knife rotors. Test results were evaluated regarding particle length,particle structure, energy consumption and capacity. Costs were calculated for the handling system of the bales from the farm orstorage site to the processing unit for disintegration and then to the digester.

All three machines managed, to different extent, to reduce particle length and damage the structure of the grass. For a goodestimation of the capacity and fuel consumption further tests are needed. The purchase of bales and transport to the plant arethe largest costs in the system. It is therefore crucial for the interest of the biogas plants to use bales if they can have themdelivered for free at the gate. If and how much the biogas plant is prepared to pay for the bales is also highly dependent on howthe silage quality affects the methane yield potential.