Feasibility study for a demonstration plant for the sustainable and economic conversion of liquid manure into specific plant additives in the circular economy – Project Innovative Liquid Manure Management (PIGM)

Challenge

Manure from animal husbandry is a valuable fertilizer. It supplies agricultural soils with organic matter and important nutrients, helping to meet the nutrient needs of plants and maintain soil fertility. On the other hand, liquid manure, just like digestate, is a non-specific fertilizer: the phosphates and nitrogen compounds needed by plants are present in undefined proportions and different concentrations. Thus, if nitrogen is needed, liquid manure fertilization also applies phosphate, which is not absorbed by the plant, but rather pollutes soil, groundwater and surface water – and vice versa.

In addition, the intensification of livestock farming and the regional concentration of farms are resulting in significant amounts of surplus manure that cannot be efficiently used as a resource in the producing regions alone. In these regions, manure is becoming a waste stream that needs to be treated or disposed of, thereby consuming energy, e.g. for transport and disposal.

At the same time, across the EU, annual excretion of nitrogen and phosphorus from livestock is sufficient to meet the EU's needs for mineral fertilizers. Overuse of synthetic fertilizers and corresponding crop yields obscure the fact that soil organic matter is being lost and not replaced. This results in a loss of soil fertility, biodiversity, lower water retention capacity and disruption of natural nutrient cycles.

Objectives and plans: Valorization of liquid manure through specific remanufacturing of the ingredients in an industrial demonstration plant

The aim of PIGM is to achieve a continuous, sustainable and economical conversion of liquid manure into specific plant additives, such as natural fertilizers. To this end, the resource- and energy-efficient BioEcoSIM process, which has been successfully developed at Fraunhofer IGB on a laboratory scale and tested on a pilot scale in follow-up projects, is to be transferred to an industrial demonstration plant. To this end, PreZero is designing and planning a full-scale single-purpose demonstration plant for the complete energetic and material remanufacturing of pig slurry and other agricultural residues into natural plant additives as part of a feasibility study. The Fraunhofer IGB is providing scientific support for the study.

Since raw slurry is significantly more difficult to process than digestate, a biogas plant is installed upstream of the BioEcoSim process in order to metabolize unwanted accompanying substances, to increase the energy yield from the liquid manure, to cover the energy needs of the plant for plant additives and to increase the economic efficiency of the overall project by selling surplus bio-methane gas and electricity (CHP).

Planning of the PIGM plant

To implement the PIGM plant, the liquid manure is first remanufactured in a biogas plant and the resulting biogas is used to supply energy to the entire plant.

The digestate from the biogas plant is broken down into individual plant auxiliary fractions in the PIGM natural fertilizer plant using the BioEcoSIM process:

• Ammonium sulphate and struvite for use as a fertilizer for plants
• The soil conditioner consisting of the solid components for humus formation
• The aqueous residual fraction of the liquid manure as irrigation water for soil irrigation

Impact: circular economy for nutrients and new value chains for rural areas

The complete recycling of liquid manure in a PIGM plant can, on the one hand, counteract the eutrophication of soils and water associated with traditional liquid manure fertilization. On the other hand, the valuable liquid manure components, in particular nitrogen and phosphate, are made available for targeted and needs-based fertilization of arable land. This reduces the production of these fertilizer components by mining or extracting them from fossil raw materials.

The results of the feasibility study serve as a basis for the investment decision and allow to win over all relevant stakeholders – especially small and medium-sized companies in the agricultural sector – in the value chain in regions with a high level of large-scale livestock farming for the process and to validate the recycling strategy.

A new value creation model for the valorization of liquid manure

Prior to the final investment decision for the construction of a corresponding plant constellation, technical feasibility, the availability of input materials and spatially related areas, as well as political acceptance and economic exploitation, must be ensured. In a multi-stage planning process, the technical requirements, the ecological and economic framework conditions and the concerns of all stakeholders, from livestock farms to land owners and municipalities to regional energy suppliers, must be coordinated.