Recycled nutrients products and fertilizers

Recycled nutrient products are manufactured from nutrient-rich by-products and waste streams from agriculture, communities and industry. Recycled nutrients can replace inorganic fertilizer products made from virgin raw materials and fossil fuels with renewable energy, while at the same time reducing greenhouse gas emissions.

Recycled nutrients are used especially in agriculture and forestry, in the forest and energy industries as well as in green and environmental construction. Ammonia used in the manufacture of nitrogen fertilizers is also needed in the metal and chemical industries, for example. Phosphorus is a limited and geographically concentrated natural resource, and its use is also expected to grow in new industries, such as the battery industry. Phosphorus is on the EU’s list of critical raw materials.

Use of recycled fertilizers and nutrients can reduce the environmental impacts of food production. In general, fertilization aims to improve plant growth by increasing the amount and/or balance of nutrients available for plants. The most common recycled fertilizer is manure, and products intended for fertilization use have so far been closer to manure than mineral fertilizers, but new, further processed products are also increasingly available and under development.

The role of recycled fertilizers in agriculture is diverse:

the carbon footprint of recycled fertilizers is smaller than that of mineral fertilizers
recycled fertilizers are not dependent on non-renewable natural resources
the processing of biomasses into recycled fertilizers can promote the transport of nutrients away from areas with nutrient surplus
in addition to nutrients, many products also contain organic matter and thus, unlike mineral fertilizers, act for both fertilization and soil improvement purposes
recycled fertilizers play a key role in regenerative farming: positive impacts on soil structure, water management, yield capacity and microbial activity.

Fertilizers, soil improvers and substrates are produced from e.g. compost and biogas plants and for some extent municipal sewage sludge.

Legal framework in Finland

Recycled fertilizers are part of recycled fertilizers products, the safety, quality and legality of which are regulated by the Fertilizer Products Act (711/2022). The objective of the Fertilizer Products Act is that fertilizer products placed on the market in Finland are safe and of good quality and suitable for plant production. The purpose of the Act is also to promote the utilization of by-products suitable for use as fertilizers products when they do not cause danger or harm to humans, animals, plants or the environment and they have positive effects on plant growth. The requirements for the ingredients and product categories of fertilizer products are laid down in the Ministry of Agriculture and Forestry’s regulation on fertilizer products (964/2023).

Fertilizing products include the following types of fertilizing product types:

fertilizers
liming agents
soil improvers
growth substrates
microbial preparations

Each fertilizing product placed on the market and imported into Finland must consist exclusively of ingredients that meet the ingredient categories of the national legislation or of the EU Fertilizing Products Regulation.

Recycled nutrients have an important role in providing energy self-sufficiency and the transition away from fossil production inputs. Developing nutrient recycling solutions that promote the green transition will create new business, jobs and export opportunities.

Sources: Ministry of the Environment of Finland, Kierrätyslannoitteet – Suomen Biokierto ja Biokaasu ry

Sewage sludges as fertilizing products in Finland

Sewage sludges used as fertilizing products shall be treated by composting, digestion, lime stabilization, ageing, thermal drying or acid and alkaline treatment. Treated sewage sludge belongs to ingredient class 10. Sewage sludges include: municipal wastewater sludges, precipitation and sealed tank sludges, property – or farm-specific wastewater treatment system sludges, dry toilet waste and sludges from wastewater treatment plants other than those mentioned above.

Quality requirements

After treatment, treated sewage sludge must meet the requirements specific to each ingredient class with regard to hygiene and impurities as well as stability requirements according to its intended use. Stability criteria have been set for composted and digested sludges. Stability criteria for digested sludges will enter into force on 1.1.2027. In addition, a fertilizing product containing sewage sludge treated as an ingredient must meet the requirements specific to the product category.

The precautionary period

The precautionary periods apply to fertilizer products produced using treated sewage sludge. During the precautionary period, plants that can be eaten fresh and whose edible parts can be in direct contact with the ground or plants whose underground parts are intended for eating may not be cultivated for human consumption or feed. A two-year withdrawal period must be followed for plants grown for human consumption and one year for feed.

Application of products containing treated sewage sludge

When using a fertilizing product on arable land, at least 90 per cent of the ingredients of which belong to the category treated sewage sludge, the concentrations of harmful substances in arable land must be examined before applying the fertilizing product. If necessary, repeat samples shall be taken every five years. The requirement to examine arable land comes from EU legislation, and it is not possible to deviate from it at the national level.

The maximum allowable amount of application of sewage sludge according to ingredient class 10 shall be 6 000 kilograms per year or 30 000 kilograms of dry matter per hectare over a period of five years. The maximum allowable amount of application shall be calculated based on the mass fraction of the sewage sludge. If the product description of the fertilizing product does not contain information on the proportion of sewage sludge, the fertilizing product is considered to be sewage sludge in its entirety. The mass share of sewage sludge in the mixture is the mass of sewage sludge divided by the mass of the whole mixture.