The second life of delicate human waste. An eco-friendly solution for the energy sector

Among the well-known renewable energy sources, such as the sun, wind, or tidal energy, one often overlooks another, almost inexhaustible source that will exist as long as humanity exists. This source is human waste, in particular feces, which is generated every day and eventually ends up in sewage treatment plants in human settlements.

At such facilities, fecal matter is mixed with biological sludge, which uses it as a nutrient medium. As the sludge grows, organic matter decomposes. After that, the sludge suspension is sent to sludge ponds, where fermentation takes place for 3-4 years. During this period, carbon is released from the sludge in the form of carbon dioxide, which has a significant negative impact on the environment. However, the problem does not end there – there is still the issue of utilization of residues after fermentation, which pose a serious environmental hazard.

A series of tests of the intensive dewatering technology for sludge slurry were conducted at the Chernihiv wastewater treatment plant. A special coagulation accelerator developed by the authors was added to the slurry (TU U 20.1-НК466211-001:2014). As a result, 7,432 cubic meters of water were removed from 12,842 cubic meters of slurry within 14 days, and the dry residue amounted to 5,410 tons. Due to the rapid dewatering, fermentation does not occur and carbon dioxide does not evaporate, which contributes to the formation of dry residue. This product resembles peat or lignite in appearance, but surpasses them in calorific value – 4,004 kcal/kg (compared to 2,900 kcal/kg for peat, 3,200 for lignite and 5,400 for hard coal).

Chernihiv, with a population of about 294,000 people, is capable of producing up to 1,000 tons of this fuel daily. This is enough to fully provide the city with heat without using gas or coal. Further implementation of the project involves generating electricity by burning sludge. For example, 100 thousand tons of sludge can power a 6 MW power generator and an additional 1 MW of heat.

The technology solves the following key problems:

• Ecology, by reducing the impact of sludge on the ecosystem, preventing further contamination of soil, groundwater and surface water through sludge maps.
• Fuel and energy – creation of an alternative energy source.
• Water management, through the efficient use of sludge, which is an adequate management of waste generated during water treatment.
• Agriculture, through the use of sludge and ash after its combustion as secondary raw materials for soil fertilization (subject to appropriate treatment).
• Engineering and waste management technologies, through the development of technologies for dewatering, recycling or reducing sludge volumes.
• Urbanism and land use, for the rational use of land occupied by silt maps.
• Environmental protection in the use of fecal sludge processing products in the reclamation of mined land.

The solution to this problem is also an interdisciplinary task that requires the involvement of specialists from various fields, including chemistry, biology, processing technologies, and economics. However, the introduction of this technology in European countries, including Ukraine, will not only improve the environmental situation and reduce greenhouse gas emissions, but also reduce dependence on energy imports. This, in turn, will help limit the aggressor’s funding, which is important for preserving Ukraine’s independence.