Anaerobic Digestion

Anaerobic digestion AD is an efficient technology well proven in industrial scale to convert organic waste in valuable resources as renewable biogas and biofertilizer. The key targets of organic waste treatment by AD are high biogas yields as well as the production of high-quality biofertilizers. Biogas is the most flexible and a storable renewable energy source that is produced continuously and independent from climatic conditions and its utilization on demand is possible if required. Biogas can be used to produce different types of energy as heat, electricity, cool or after further upgrading to biomethane it can be used as biofuel. It is important to select the most economical way of biogas utilization with the begin of an anaerobic digestion project.

Biomethane Production

Biogas is produced in anaerobic digestion plants from organic waste. The composition of biogas depends on the type of organic waste that is treated, and the methane concentration of biogas can vary between 55 and 75 Vol.-%. The other essential component in biogas is CO2 with a concentration in a range of 24-44 Vol.-%. There are still up to 2 Vol.-% other components in biogas such as oxygen, nitrogen and hydrogen.

It’s basically advisable to use substrates that produce during anaerobic digestion process biogas with the highest possible methane content. The energetic recovery of biogas can be carried out in various ways e.g. for the generation of electricity and heat in CHP-plants. But biogas utilization in CHP plants makes only sense if the produced heat can also be used. Otherwise the energy efficiency and the economics of biogas utilization is poor. Therefore, the most economical type of biogas utilization must be reviewed and defined for each project.

In many projects it makes sense to further process biogas by separating CO2 and to produce bio natural gas, or so called biomethane. With an efficient biogas upgrading technology > 99% of the methane contained in the biogas is obtained and the biomethane produced usually has a methane concentration higher than 98 %. This makes biomethane a quality comparable to natural gas.

The different technical steps of the value chain from biogas to biomethane production and grid injection into natural gas grid:

A very interesting option is also the use of biomethane as fuel for vehicles (buses, cars, trucks, ships) to substitute the use of fossil fuels as diesel. Thus, not only the emissions of CO2 but also of other pollutants as fine dust, nitrogen oxides are drastically reduced. Fuel types are either bio-CNG (compressed biomethane) or bio-LNG (liquified biomethane). Bio-CNG is traditionally used for cars and buses whereas bio-LNG is used for heavy duty trucks and ships. Our activities include the planning of new plants as well as integration of biogas upgrading plants in existing anaerobic digestion plants.

We support our customers in the planning and realization of biogas upgrading systems in many ways. These include:

• Feasibility studies for technology selection
• Clarifications of interfaces to anaerobic digestion plant and to natural gas grid operator
• Tender documents for technology procurement
• Supplier bid evaluation
• Preparation of documents for approval procedures
• Supervision of installation and commissioning

Waste Recycling

Municipal solid waste (MSW) includes indeed a high percentage of organic fraction but also valuable resources that can be recovered in mechanical sorting plants. In addition to the recovery of raw materials, the treatment of the organic fraction is of central importance in order to avoid the emission of climate-damaging gases caused by the biological decomposition of organic constituents on landfill sites. The organic fraction of MSW can be used sensibly by anaerobic digestion to produce renewable biogas. If both technologies are combined it is a so-called Mechanical-Biological-Treatment plant (MBT plant).

It is technically possible to separate from MSW following in mechanical sorting plants raw materials as:

• Plastic (PP, PS, PET, PE, HDPE, LDPE, PVC etc.)
• Glass• Paper
• Cardboard
• Fe-metals
• Non-Fe-metals

For the technical solution it is important to identify the markets for the recyclables and the expected revenues.

The mechanical sorting of MSW includes different process elements:

• Crushing
• Screening
• Ballistic separation
• Wind shifting
• Optical sorting
• Fe-Metal separation
• Non-Fe-Metal separation
• Pressing of recyclables

The intelligent combination of technically sophisticated individual processes enables the separation of municipal solid waste characterized by a very heterogeneous composition, into high-quality material flows that can be recycled and are returned to the material cycle. As a result, limited available raw materials on the market and fossil fuels used for the material production can be saved. Efficient mechanical sorting systems ensure high recycling rates of MSW and contribute significantly to landfill diversion.

Today, modern mechanical sorting systems of MSW already fulfil important functions in environmental and climate protection in many respects.

Plant Optimization

Waste treatment plants are operated over many years and therefore there is usually a need to carry out optimizations on the plants.

A. Reasons for plant optimization

The reasons for plant optimization needs are diverse:

1. New legal framework
2. New waste streams
3. Modified waste management strategies
4. Change in waste composition
5. Technical problems
6. New technologies

B. Objectives of plant optimization

The main objectives of plant optimization measures are:

1. Improving the efficiency and profitability of the plant
2. Capacity increase
3. Compliance with new legal requirements

C. Priorities for optimization

Our priorities and experience in optimizing waste treatment facilities:

1. Alternative energy use concepts for biogas (biomethane, bio-CNG, bio-LNG, ORC)
2. Minimizing rejects fractions from waste treatment (by mechanical or biochemical treatment)
3. Increase in biogas yield (mechanical and biochemical biomass treatment, alternative energetic waste fractions)
4. Reduction of energy consumption (substitution of energy-intensive machines)
5. Technology optimization and new technologies (treatment, pasteurisation, biogas conditioning, biogas utilization, digestate treatment)
6. Digitization

D. Inventories for economical optimization

In particular, measures to improve the economic viability of waste treatment plants are of great importance to plant operators. In several steps, the optimization proposal is developed after the inventory of the plant has been taken up.

We support our customers from the inventory to the implementation of the optimization measures with the following activities:

1. Inventory
2. Identification of optimization potential
3. Feasibility
4. Evaluation of funding opportunities
5. Implementation (planning, implementation, commissioning)

There are numerous state funding programs that support those activities that contribute to climate protection or improve resource and energy efficiency. We check for our customers which funding programs can be used to optimize investments and in this context take over the contact and application with the relevant project promoters.