This article deals with the actual problem of high nitrate content in vegetables and fruits. The literature review describes the consequences of increased nitrate concentration in the human body and the diseases associated with it. Different countries have different standards for the content of nitrates in agricultural products and the maximum permissible daily doses. The increased content of nitrates negatively affects human health, so it is necessary to maintain strict control over compliance with the concentration standards to the maximum permissible concentrations. Research was carried out on the content of nitrates in vegetables and fruits purchased in the trade networks of the two countries in Russia and Mongolia. The measurements were performed using a portable nitrate -tester SOEKS. As a result of the study, it was found that agricultural products purchased in the trade network of Ulan Bator (Mongolia) meet the established standards, in fruits purchased in St. Petersburg (Russia) in excess of tangerines 1.5 times and 1.6 times. The products that were found to contain excess nitrates were imported from China.

In this paper, we consider the process of producing biogas with a high methane content when used as a co-substrate for fermentation of plant residues of microalgae. Microalgae Chlorella sorokiniana are a valuable source for obtaining valuable components such as lipids, pigments, proteins, chlorophyll and others. After the extraction of valuable components, residual biomass is formed, which requires further disposal. In this experiment, the digestion process is carried out using an inoculant -lyophilically dried activated sludge from sewage treatment plants in Hamburg in the amount of 450 ml and residual biomass of the microalga Chlorella sorokiniana in the amount of 2.1 g. The studies were carried out in the Anaerobes Test system AMPT-II system. Fermentation produces 205 ml of methane gas.