Sewage sludge from municipal wastewater treatment plants is a growing problem, as
there is currently no clear vision of how to use sludge sustainably in agriculture or any
other sector in an environmentally and economically sound manner. Currently,
incineration is one of the most widely used methods for sewage sludge removal. The
aim of the thesis was to determine the benefits and potential risks of biochar produced
from sewage sludge. The literature review includes studies that have studied the effects
of adding biochar from sewage sludge in field experiments. Researchers who
investigated the effects of the addition of biochar from sewage sludge on the uptake of
potentially toxic metals (PTM) in plants reported that the composition of the input
material and pyrolysis temperature had the greatest impact on biochar preparation, as
well as the dose of biochar. However, in general, excessive PTM levels in useful plant
parts do not occur, except at higher rates of biochar, i.e. 15 tons dry matter and above
per ha. The results show that biochar from sewage sludge can easily replace mineral
fertilizers because it contains sufficient amount of macro- and micronutrients. However,
biochar cannot increase the content of nutrients that are deficient in the soil to an optimal
level. We must be careful when using biochar from sewage sludge, as the safety of the
crop depends largely on the basic material and its background (PTM content in sewage
sludge). It also follows that it is difficult to determine the safe amount of biochar added.
It is necessary to take into account the PTM content in the soil to which the biochar will
be added, and the presence of PTM in biochar from sewage sludge.
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