The conditions for efficiently recycling biomass in terms of materials and energy vary throughout the world. However, one issue all countries share is the more or less severe contamination of biomass with non-biogenic substances, such as packaging plastic.
The DRM separation mill is at the heart of our plant design. This is supplemented with additional components to empty and clean the containers, store the substrate and provide transport. A prerequisite for machine separation with the DRM is the size, type and quantity of contaminants in the input material. Experience has shown that the separation of objects measuring 150 x 200 mm does not cause any difficulties. Large foreign objects made of wood or metal, on the other hand, require the equipment to work harder and may even require manual (pre-)selection.
Overview of the process steps:
Biowaste is collected regionally and internationally in various containers. The volume of a receiving container must be large enough to buffer a sufficient quantity. Robust technology is important for removal from receiving. Ideally, the biowaste is already thoroughly pre-homogenised in the hopper, which opens large (re)packaging and ensures a uniform substrate supply for the actual separation. We adapt this receiving system precisely according to the planned throughput and the expected waste composition. Robust, wear-resistant screws are used, which are precisely matched to the throughput of our DRM 800 separation mill. Installation at ground level is possible, as well as in a basement optimised for offloading the vehicles. The container can be supplemented with walkable covers and flaps for vehicle acceptance.
The predominant variant of receiving containers are bottom screw feeders.
Triple-screw bottom screw feeders, e.g. for packaged food waste, with a volume of approx. 60 m³ are common. However, sizes of 15 m³ and for wheel loader filling up to approx. 120 m³ are also possible. In general, stainless steel is used.
Reliable stainless steel screw conveyors transport the biowaste from the receiving container to the DRM 800 mill. The material strength and design of the screws ensure durability and uniform dosing without clogging, thus guaranteeing fault-free operation over the course of the year and with changing volume flows.
The biowaste is brought in containers for waste treatment. This often includes individual large refuse containers delivered by vehicles. Depending on the number of large refuse containers per day, it makes sense to automate the emptying process. Single and multiple tipping stations are possible. As a rule, there should be an automatic pre-rinse after emptying to minimise the transport of biowaste into a downstream container washing machine. There are two possibilities: hoisting over a container placed at ground level or emptying into a recessed container. If the throughput is high, bin handling, including removal, can be fully automated. We choose the optimal variant in close coordination with our customers and taking into account the on-site situation.
The input material is transported to the grinding chamber of the DRM double rotor mill via a receiving container and a screw conveyor. The DRM separation mill is designed for the reliable separation of the biogenic content from foreign matter or contaminants from various waste streams. The goal is the optimal cleaning of the respective substrate from the very beginning of the process. The special design enables high separation performance while greatly reducing the energy consumption per bin. This makes the high-performance DRM technically as well as economically appealing to customers who want to separate larger quantities of waste continuously.
The foreign matter separated out by the separation mill is usually disposed of thermally. The liquid content in the foreign matter leads to increased costs. That is why our screw press removes moisture. Additional separated liquids are collected and passed back to the organic fraction. The screw press consists of a solid stainless steel screw surrounded by a segmented basket sieve. This basket sieve separates out liquids. In terms of performance and design, the screw press is always adapted to the type of waste and the throughput of the DRM separation mill.
Refuse containers must be cleaned after they are emptied so that they can be returned to households or supermarkets hygienically. For washing, the following factors are decisive: throughput, effectiveness, as well as energy and water consumption. Washing machines can be filled either manually or automatically directly from the tipping stations. Generally speaking, bins are transported to the clean area during or shortly after washing. There, the bins can be automatically issued, stowed or removed manually and are available to be reloaded onto the vehicle. We adapt the washing machine technology to suit the required throughput.
It can make sense to supplement our proven DRM technology with further processing steps. These may include screening or dissolving techniques before processing. After processing, glass and “grid” separation can come into play. If the biowaste is very heterogeneous or very large foreign substances need to be dissolved, a shredder can be used. The use of a bag opener is always useful when very large packaging needs to be opened. It stops at large contaminants, which can be easily removed by hand. The bag opener is usually integrated into the hopper in the interest of “lean” plant engineering, which positively affects a plant’s separation result. Star screens can be used instead of a crusher if large substances need to be continuously discharged from the process without being crushed.
“Our plant design allows us to ensure the optimum separation of biowaste and packaging. This is a prerequisite for optimally recycling biomass in terms of materials and energy.”