Heavy Metal Content in Substrates in Agricultural Biogas Plants

Abstract

The content of heavy metals in soil should be continuously monitored, especially in organic crops. Exceeding the permissible concentrations of these elements may lead not only to inhibition of plant growth but also to ingestion into the organisms of animals that feed on these plants. Heavy metals usually enter the soil via precipitation or manure. There is a noticeable increase in interest in digestate for fields fertilization. Therefore, the authors decided to test the heavy metal content in substrates (slurry and solid input) and digestate. The 15x3 samples tested showed that only trace amounts of heavy metals were present. The study shows that the content of these elements in the digestate is not the sum of the elements supplied to the digester with the substrates. In most of the samples tested, lead concentrations did not exceed 5 mg‧kg−1. The lowest amounts of cadmium (an average of 0.28 mg‧kg−1) were observed in the slurry, and the highest (an average of 0.34 mg‧kg−1) in the solid substrate fed to the digester. Slurry had the lowest mercury and cadmium contents (average 0.012 mg‧kg−1and 5.8 mg‧kg−1). The highest concentration of chromium was registered in the digestate (average 3 mg‧kg−1) and this was on average 0.3 mg‧kg−1 higher than the feedstock and 0.5 mg‧kg−1 than the slurry

The Impact of Biochar Additives and Fat-Emulsifying Substances on the Efficiency of the Slaughterhouse Waste Biogasing Process

“…At the same time, it has very high potential in the context of energy use and in the context of returning elements to biocirculation [39]. Ware and Power [49] indicate that the potential for methane production from mixed cattle slaughterhouse waste is 690 dm 3 /kg of waste. The fermentation of waste containing fats is associated with technological problems that affect the methane fermentation process.…”

“…Modern technologies for the biogasification of slaughterhouse waste without co-fermentation are characterized by relatively low efficiency. Galván et al [53] calculated the efficiency of biogas production from pig slaughterhouse waste as 169 dm 3 /kg fresh mass. The total biogas yield in the control fermentor (C) was observed at approximately 360 dm 3 /kg.…”

“…In the period 1971-2001, global energy consumption doubled. By 2040, it is estimated to increase by another 48% [1][2][3]. Despite the continuous development of technologies that reduce waste introduced into the environment, the modern global economy is still characterized by a low level of waste recycling, both in terms of elements and energy [4][5][6][7].…”

Agricultural Micro Biogas Plants as a Factor in Farm Development—A Case Study

“…When building a biogas plant, the location plays a key role, which mainly depends on the availability of input materials (type of farm), the availability of the electricity grid, and the distance from urbanised areas (due to the potential impact of the biogas plant on noise and odours) [11][12][13].…”

Influence of the Parameters of an Agricultural Biogas Plant on the Amount of Power Generated

“…Hence, the co-digestion of manure and other feedstocks is often used (to improve biogas yield) [66][67][68]. The digested animal manure (digestate) can be used as full-fledged manure [69][70][71].…”