There are a range of options available for processing poultry litter. In the Netherlands over one-third is currently burned in the incinerator operated by BMC Moerdijk to generate electricity, with the ash being used as a fertilizer substitute. BMC Moerdijk commissioned CE Delft to assess the environmental impact of thermal conversion of the litter at their facility and compare it with that of eight alternative processing routes, like Co-digestion. Composting or direct application of the raw litter.
The nutrient balance, considers the presence of (effective) organic matter and the nutrients nitrogen, phosphorus and potassium before and after processing. It shows that in a wood-fired biomass power plant all these useful resources are lost. For thermal conversion the organic matter and nitrogen are lost. But the amount of phosphorus and potassium in the end-product is approximately the same as in the other routes. Phosphorus and potassium are finite resources and therefore important from the perspective of a circular economy and resource conservation.
The LCA study shows that all the routes with power generation have environmental benefits. The processing routes with the least environmental impact are:
1. Thermal conversion at the BMC Moerdijk plant
2. Co-firing in a wood-fired biomass power plant
3. Thermal conversion on a poultry farm
All the routes generating no electricity or heat have an environmental impact. The LCA with system expansion shows that the BMC route in combination with the production of nitrogen and organic matter in another way, has the least environmental burden, thus confirming the results of the basic LCA.
When the two parts of the study are combined – the nutrient balance and the LCA – thermal conversion at BMC and on a poultry farm both score positively in environmental terms. If thermal conversion on a poultry farm can be combined with effective use of most of the heat, this route scores best environmentally.