How safe are alkaline batteries as raw material for fertilisers?
Let's talk about it.
Alkaline batteries contain high amounts of zinc and manganese, around 50% of their weight. Both micronutrients are important for plant nutrition, making batteries a viable and widely available source of micronutrients. There has been a global interest in turning this otherwise wasted and potentially harmful raw material into useful and ecological products.
To make alkaline batteries into raw material for fertilizers, as well as for other products, the batteries are crushed into a material usually called black mass or battery mass. This is an ideal raw material to produce zinc and manganese foliar fertilizer but should not be used directly for soil fertilization.
Black mass is made up of crushed alkaline batteries from which the ferrous metals have been magnetically separated. The resulting mass is a mixture of zinc, manganese, steel, plastic, paper, graphite as well as some harmful metals such as nickel. Some of these contents can be harmful not only to the environment but also to the plants themselves and the food chain they pass on to. This makes processing and purification the highest priority when producing a fertiliser out of black mass or from other similar metal powders made from batteries.
When household batteries are collected and sorted, some of the other battery fractions like nickel-cadmium and lithium-ion batteries can also enter the battery stream, adding various unwanted and harmful metals such as nickel and cadmium into the mixture. Additionally, the steel covers used in alkaline batteries are made of nickel-plated steel, which also increases the nickel content of black mass.
The harmful nickel and cadmium residues become mixed with the mass in the crushing process. Most of the nickel-plated steel is removed from the resulting crushed mass via magnetic separation, but some of the nickel remains dissolved in the BM along with microplastics, which are also harmful to the environment and the food chain.
Both the nickel and cadmium content are overseen by the authorities because the EU fertilizer legislation places strict limits on these harmful metals. If their concentrations are too high, the product cannot be used as a fertiliser in Europe. The amount of nickel in black mass can be ten times the concentrations allowed by fertiliser legislation. For cadmium, the concentrations can exceed the allowed amounts by a factor of a hundred or more.
Dumped in the landfill, used batteries turn into a hazardous waste.
ZM-Grow™: Tracegrow's patented solution
These challenges have been recognized and studied by Tracegrow, and we have developed an efficient and reliable method of turning black mass into a pure and safe product, ready for use in fertilisation. In our leaching process, BM is turned into a liquid where zinc and manganese exist as plant-available sulphates.
This liquid is then thoroughly filtrated, removing the microplastics and graphite from the solution. Nickel and cadmium need to be extracted from the solution with other means. For this purpose, Tracegrow developed and patented a separate purification process where nickel and cadmium residues are removed from the solution and collected for reuse.
The end product is ZM-Grow, a purified foliar fertilizer that fulfills the strict purity requirements of European and other regions fertilizer legislation and is available to be sold in the EU as well as other parts of the world. Tracegrow’s patented process is first of its kind in the world and a proven method of turning black mass into a safe and environmental product, certified for organic farming. The process has won Tracegrow environmental awards.
Improved nutrient availability in ZM-Grow
Soil fertilisation using traditional micronutrient fertilisers is inefficient compared to the foliar application, because soil conditions like high pH and high organic matter content may bind the micronutrients into an unusable form.
This is also an issue with the zinc and manganese content of BM or the metal powder if they are left in their untreated state.
Zinc and manganese in BM are in a metallic form, or as oxides, dioxides, and hydroxides. Most of these forms are not readily available for the plants to utilize. For this reason a large portion of these micronutrients can be wasted if they are used in this state.
Because ZM-Grow™ is a sulphate solution, the nutrients absorb directly into the plant leaves. Because of the sulphate form and the foliar application, the micronutrients are in an available form for the plants to use and are not at risk to be bound into the soil. However, tissue tests have shown that the most effective way of increasing the nutrient content of zinc and manganese in plants is combined fertilization through the soil and foliar fertilization. A comparison between foliar-applied sulphates and oxides/carbonates is presented in graph 1.
Standart deviation ±8%
Source: Influence of formulation on the Culticular Penetration and on Spray Deposit Properties of Manganese and Zinc Foliar Fertilisers; Alexander and Hunsche 2016)
Graph 1. Absorption difference of foliar sulphates and carbonates/oxides
Tests have proven that it gives high micronutrient boost for plants, and farmers have experienced high yield increases: even 1500 kg/ha (27 %) more crop.
Soil Conditions And Micronutrients
Macronutrient fertilisers (NPK-fertilisers) are commonly given to plants as soil-added granules. The granules slowly break down in the soil, and the nutrients are absorbed through the plant’s roots.
With micronutrients, such as zinc and manganese, application through the soil can be affected by various soil conditions.
The Product has been tested in Finland, England, Italy, the USA, and other countries with good yield increases, and positive feedback from farmers.
Has thus far been tested for wheat, oats, barley, grass, corn,
citrus, avocado, cotton, tomato, and potato.