Agricultural composting: cooperation between farmers and scientists
Written by: Claas Menke, Lukas Huhn, Ina Körner, TUHH (April 2022)
Intensive cooperation has started with two German agricultural companies. Both are carrying out field composting on their farms. The smaller one processes about 800-900 tons substrate per year in a static way. The substrates are mainly own horse manure with additions of biowastes from various external sources. The larger company carries out a composting with regular turning for up to 4000tons a year of cow manure together with green waste from municipal sources.
TUHH has joined negotiations of the farmers with regional authorities regarding the approval of their composting sites. The substrate amount showed to be a major issue for regulatory approvals. TUHH also discussed issues regarding composting optimization and co-substrate choices with the farmers. Furthermore, first compost and soil samples were analyzed. This pre-results showed suitable water, pH and organic matter contents of the composts. But also the possibility of a relocation of nitrate and ammonia into soil layers up to approximate 1.5m below the windrows. A detailed analysis of nitrogen emissions into groundwater and atmosphere was initiated.
An experimental design with adsorptive layers below the windrows was developed. Further suggestions for an operation with reduced emissions included: a quick processing of manure substrates, adjustments of the initial mixtures for a well substrate structure, the batch-wise movement of composting piles on the site, the use of deep-rooting annual plants for nitrogen absorption from soil, the coverage of windrows with foils or a roof (with solar panels) to avoid leaching during heavy rains. And the drainage of rainwater from the site into a pond.
Open windrows in agriculture. The windrows are prepared from manure and municipal green waste.
The foreground shows a marking for a nitrate sampling point to determine background content in soil.
(Foto: Menke, TUHH, 2021).