Through hydrothermal carbonization (HTC), liquid and pasty materials can be efficiently processed for nutrient recovery and fuel production.
To give sludge or other very liquid starting materials meaningful use, they must first be mechanically dewatered and then thermally dried. With conventional methods, this process is very energy-intensive.
The HTC process imitates the natural formation of coal. With state-of-the-art HTC technology, AHT can convert very moist and even liquid substances such as sludge, manure, fermentation residue, seaweed, or pomace effectively into so-called hydrochar within a few hours. Valuable substances such as phosphorus and nitrogen can be separated in the watery phase.
Hydrothermal carbonization can offer an economical alternative. Without energy- and cost-intensive pre-treatment, a liquid substance is efficiently converted into a coal-like product within a few hours.
How it works?
The process of hydrothermal carbonization (HTC) involves the preparation of the liquid input material, such as manure or sewage sludge, so that it can be easily pumped (<30% total solids). Valuable resources like phosphorus and nitrogen are transferred to the aqueous phase in this process and can be efficiently recovered using heat recovery.
Next, the moist material is transformed into hydrochar at a temperature of about 180-220°C and a pressure of 20 to 35 bar, in the absence of air. The HTC process only takes a few hours and takes place in an aqueous environment, eliminating the need for energy-intensive drying of the input material beforehand. After the treatment, the hydrochar can be easily and efficiently mechanically dewatered to up to 70% dry matter, making it possible to use the materials in an energy-positive way.
The HTC process used by AHT employs an innovative heating system and an efficient heat recovery system, minimizing energy consumption during the carbonization process. The resulting material is then briquetted, resembling a lignite briquette in form and structure, and can be used on-site or transported.
AHT emphasizes the concept of decentralization, allowing for energy-positive utilization of sludge and manure to take place locally, rather than transporting wet sewage sludge over long distances to incineration plants. By using the HTC-char in their own bio power plants, municipalities can reduce their dependence on external energy sources and produce electricity and heat on-site.
Impact: Use of sewage sludge
Through the HTC process, the waste product sewage sludge, which usually needs to be disposed of at a high cost and using additional energy, becomes a valuable resource that generates revenue for municipalities. Transport routes and costs are minimized, jobs and value creation remain completely within the region. Future legal requirements, such as those regarding the use of sewage sludge, are also met.
A comprehensive assessment of saved disposal costs, reduced municipal energy costs, and the possible self-use of generated heat in the municipal sector results in highly interesting business models, which are already feasible on a small scale from 1 ton/h. This corresponds to the amount generated by a sewage treatment plant serving approximately 20,000 people.
With a comparable approach, agricultural businesses with high amounts of manure or digestate can benefit from the HTC technology.
Under suitable conditions, the entire concept can be implemented without investment by the municipality or the company. AHT is also available as a joint venture partner for the implementation of these regional concepts.