# Influence of the Parameters of an Agricultural Biogas Plant on the Amount of Power Generated
## 2 Materials and Methods
Therefore, in the absence of feeding the digester with bacterial strains (e.g., by feeding slurry), a retention time of less than 20 days is not recommended. Daily, part of the digested slurry was pumped from the digestion reactor into the digestate tank. The dose of pumped digestate was controlled automatically and depended on the amount of biogas produced, which in turn depended on the parameters of the slurry fed in. A pressure sensor determined the charge level in the reactor. Once the process of pumping out the digestate was complete, when the pressure dropped below the set value, a new slurry was pumped out of the collection channel to compensate for the substrate's shortfall. The volumetric load is a parameter that determines how many kg of dry organic matter should be supplied to the digester about its volume, described by the following relationship [72]:  
\[B=\frac{m\times c}{V_{R}} \tag{2}\]  
where _B_--volume load of the digester, \(V_{D}\)--daily volume of slurry flow into the digester [m\({}^{3}\)/day], \(C_{D}\)--concentration of organic dry matter in the substrate [kg d.m./m\({}^{3}\)], and \(V_{R}\)--active volume of the digester [m\({}^{3}\)]. It is one of the critical process parameters determining the amount of biogas produced. Daily biogas production increases until the volume load limit is reached. Once this limit is exceeded, biogas production decreases despite the more significant amount of raw material available, which is related to the phenomenon of chamber overload. Therefore, it is vital to determine the optimum chamber load, which allows for efficient and economical methane production. A relationship describing the biogas production potential of a digester, taking into account many variables, was developed by [PERSON] et al. [73] as follows:  
\[B_{G}=\frac{0.5}{HRT}[C_{0}-C_{T}(x,t)]\times V_{R}\times\frac{T_{a}}{T_{0}} \tag{3}\]  
where _B_G--daily biogas production [kg/day], _HRT_--hydraulic retention time [day], \(C_{0}\)--organic dry matter input (\(C_{0}\) = 0.863. s.m.) [kg/m\({}^{3}\)], \(V_{R}\)--active volume of the digester [m\({}^{3}\)], \(T_{0}\)--assumed fermentation temperature [K], \(T_{a}\)--273.2 [K], and \(C_{T}\)(\(x\),\(t\))--total degradation of the substrate in the digester [kg/m\({}^{3}\)] described by the relation  
\[C_{T}(x,t)=\frac{C_{0}\cdot K\cdot e^{-1/k}}{\mu_{m}^{2}\cdot V_{R}\cdot t} \times\left\{(V_{R}\times\mu_{m}-2\times v\times k)\times\left[1-e^{-\mu_{m} \times\frac{t}{k}}\right]+t\times v\times\mu_{m}\times\left[1+e^{-\mu_{m} \times\frac{t}{k}}\right]\right\} \tag{4}\]  
where _v_--daily flow of slurry into the digester [m\({}^{3}\)/day], \(t\)--maximum hydraulic retention time for decomposition at a specific point [day], \(K\)--kinetic parameter experimentally determined by [PERSON] (\(K\) = 1.26), and \(\mu_{m}\)--daily bacterial growth. Using Equation (4), the total degradation of the substrate can be calculated in addition to biogas production. The model uses an equation that makes it possible to describe the growth rate of microorganisms. It has been validated by numerous experiments with excellent results (the results overlapped a high percentage with those obtained experimentally) [74]. The main medium studied in the agricultural microgas plant was electricity. Therefore, the priority was maintaining its production at the highest possible level. Measurements of the parameters describing electricity at the point of connection of the biogas plant to the electricity grid were performed using the SONEL PQM-701 electricity quality analyser (Sonel, Swidnica, Poland).