Biogas residue parameterization for soil organic matter modeling

Abstract

A variety of biogas residues (BGRs) have been used as organic fertilizer in agriculture. The use of these residues affects the storage of soil organic matter (SOM). In most cases, SOM changes can only be determined in long-term observations. Therefore, predictive modeling can be an efficient alternative, provided that the parameters required by the model are known for the considered BGRs. This study was conducted as a first approach to estimating the organic matter (OM) turnover parameters of BGRs for process modeling. We used carbon mineralization data from six BGRs from an incubation experiment, representing a range of substrate inputs, to calculate a turnover coefficient k controlling the velocity of fresh organic matter (FOM) decay and a synthesis coefficient η describing the SOM creation from FOM. An SOM turnover model was applied in inverse mode to identify both parameters. In a second step, we related the parameters k and η to chemical properties of the corresponding BGRs using a linear regression model and applied them to a long-term scenario simulation. According to the results of the incubation experiment, the k values ranged between 0.28 and 0.58 d-1 depending on the chemical composition of the FOM. The estimated η values ranged between 0.8 and 0.89. The best linear relationship of k was found to occur with pH (R2 = 0.863). Parameter η is related to the Ct/Norg ratio (R2 = 0.696). Long-term scenario simulations emphasized the necessity of specific k and η values related to the chemical properties for each BGR. However, further research is needed to validate and improve these preliminary results.

Biogas production and changes in soil carbon input - A regional analysis

“…The decomposition rate coefficient k describes the rate of organic matter decay and the synthesis coefficient η describes SOM creation from BGR. These values were calculated from the pH and C/N ratio according to Prays et al (2017).…”

“…In our model, the higher residence time is a consequence of the improved transfer of carbon from fresh organic matter to the SOM pools. The SOM synthesis coefficient η of BGR is higher than that of cattle slurry or manure, and thus its contribution to SOM is higher (Prays et al, 2017). Numerous studies have compared BGRs with other organic amendments (Abubaker et al, 2013a;Abubaker et al, 2013b;Möller and Stinner, 2009;Stumpe et al, 2012) and concluded that there is no long-term negative effect on the SOC if manures are anaerobically digested.…”

“…For the calculations of Crep every source of FOM has its specific substrate use efficiency parameter (η) characterizing the potential quality of the substrate for the formation of new SOC (Franko et al, 2011). The substrate use efficiency of biogas digestate was determined according to (Prays et al, 2017). For the calculation of CFOM and Crep only arable land has been considered and permanent grassland has been left out.…”

Long-Term Impact of Biogas Production on Soil Organic Carbon Storage

“…The decomposition rate coefficient k describes the rate of organic matter decay and the synthesis coefficient η describes SOM creation from BGR. These values were calculated from the pH and C/N ratio according to Prays, Sänger, Dominik, and Franko (2017).…”

“…In our model, the higher residence time is a consequence of the improved transfer of carbon from fresh organic matter to the SOM pools. The SOM synthesis coefficient η of BGR is higher than that of cattle slurry or manure, and thus its contribution to SOM is higher (Prays et al, 2017). Numerous studies have compared BGRs with other organic amendments (Abubaker, Cederlund, Arthurson, & Pell, 2013;Abubaker, Odlare, & Pell, 2013;Möller & Stinner, 2009;Stumpe et al, 2012) and concluded that there is no long-term negative effect on the SOC if manures are an aerobically digested.…”