Possibilities of Using Liquids from Slow Pyrolysis and Hydrothermal Carbonization in Acidification of Animal Slurry

Pyrolysis and hydrothermal carbonization (HTC) are gaining increasing interest in the context of biomass valorization. However, these processes yield a liquid fraction with an acidic pH value challenging to productize. In this paper, the possibility of replacing concentrated acids in acidification of animal slurry with organic acids derived from thermochemical conversion of various biomasses was investigated. The acid composition of four pyrolysis and one HTC liquid fraction were characterized using capillary electrophoresis and their total acidity determined titrimetrically. The amount of each liquid needed to reduce the pH of pig and cattle slurries to 6.0 and 5.5 were recorded. The total acidity of pyrolysis liquids varied highly (850-2560 meq l-1) depending on the biomass. For HTC liquid the total acidity was low (220 meq l-1). The most concentrated liquid, which showed greatest potential for practical use, was derived from pyrolysis of willow wood. Its required application rate for decreasing the pH of the slurries from >7.5 to 6.0 was 20-50 l t-1. This study suggests that there is a possibility of using liquids from pyrolysis process for acidification of animal slurries. Producing more concentrated liquids, further concentration of these acidiferous streams and the effects of the liquid addition on the properties of slurry are worth further studying