Phosphorus forms and lability of organic matter during anaerobic digestion of swine manure

Abstract

Understanding the dynamics of the organic matter and nutrients in pig manure submitted to anaerobic digestion is important to assist in decision-making regarding the use of anaerobic biofertilizer in agriculture. Accordingly, this study was carried out with the objective of evaluating the changes in organic matter, quantified as the content of carbon in the humic and oxidizable fractions, and in the content of the organic and inorganic forms of phosphorus in the solid fraction of the manure, as a function of digestion time in anaerobic reactors. Evaluations were carried out after 7, 14, 21, 28, 35, 42, and 49 days of digestion, and the results were compared to the raw manure. Changes in organic matter occurred mostly in the labile fractions (fulvic acid and the F1 fraction), the content of which underwent a reduction, favoring the accumulation of more recalcitrant fractions in the final biofertilizer (humic acid and the F2, F3, and F4 fractions). Total P content did not change throughout the digestion process. However, the size of inorganic fraction of water-extractable P decreased by 16.7% after 49 days of digestion, as it was consumed by the decomposing microbiota to form stabilized organic matter, which accumulated along with the more recalcitrant fractions of P in the final biofertilizer. Therefore, the use of swine manure-derived anaerobic biofertilizer has less risk of environmental contamination with excessive P than the direct application of raw manure to the soil.

Challenges and Opportunities in Biofertilizer Commercialization

“…Consumers increasingly seek products produced using environmentally friendly practices, and biofertilizers can help meet this demand. Additionally, government initiatives and regulations promoting sustainable agriculture and reducing chemical inputs have further boosted the adoption of biofertilizers [3].…”

“…Biofertilizers have gained attention for various applications, including agriculture, bioremediation, and ecology [2]. These microbial-based fertilizers offer a promising alternative to hazardous chemical fertilizers, contributing to achieving sustainable agriculture goals [3]. Agricultural policies promoting environmentally friendly products, such as biofertilizers, have become increasingly important in recent years [4].…”