| In recent years,with the rapid development of large-scale biogas projects,a large number of biogas digestate has been generated.As of2019,the annual output of biogas digestate in China has exceeded 4×10~8tons,which has become a difficulty restricting the development of the industry due to problems such as large quantity,high transportation costs,and difficulty in meeting standards.In this paper,focusing on the resource reuse of biogas digestate,the operating conditions of solid-liquid separation equipment for fermentation residues of large-scale engineering biogas enterprises were optimized,and related studies were carried out on the biogas liquid soaking and fertilization of rice,the cultivation of Agaricus bisporus in the biogas residue mulch,and the preparation of seedling substrate from biogas residue compost after solid-liquid separation,in order to broaden the utilization channels of biogas residue digestate.The specific results of the study are as follows:(1)Aiming at the solid-liquid separation needs of fermentation residues of biogas engineering of Linhai Ecological Technology Co.,Ltd.,Funan County,Anhui Province,the operating parameters and separation effects of solid-liquid separator(SLJ-7)and horizontal screw discharge sedimentation centrifuge(LW450)were investigated.The results showed that when the total solids content of the biogas fermentation overflow was5.62%and the grid pore size of the solid-liquid separator was 0.5 mm,the two-stage solid-liquid separation efficiency was the highest,and the processing capacity of the first-stage digestate and first-stage biogas liquid were 866.48±18.55 kg/h and 11133.52±18.55 kg/h,respectively,and the solid recovery rate were 42.58%.The treatment capacity of secondary biogas residue and secondary biogas liquid were 1829.8±6.90kg/h and 18170.20±6.90 kg/h,respectively,and the solid recovery rate was 50.30%.The electricity consumption of the recovered digestate were6.50±0.14 k W·h/t and 16.81±0.06 k W·h/t,respectively,and the total nitrogen,phosphorus and potassium could be effectively recovered.(2)The effects of biogas liquid on rice seed soaking and fertilization before and after treatment as the biogas liquid treated by microalgae were discussed,.The results showed that the effects of biogas liquid on rice seed soaking were significantly improved after microalgae treatment,and the germination potential,germination index and vitality index were increased by 176.80%,32.80%and 74.00%,respectively.Compared with the untreated biogas liquid,the microalgae treatment could effectively improve the fertilizer efficiency of biogas liquid,when50%concentration of the biogas liquid treated by microalgae was used as base fertilizer,the root number,root length,root fresh weight and root vitality of rice seedlings increased by 62.50%,24.80%,42.20%and44.9%,respectively,and the seedling height,fresh weight and chlorophyll content increased by 26.5%,20.4%and 102.5%,respectively.On this basis,25%～50%concentration of the microalgae treated biogas liquid was continued spraying as foliar fertilizer,and rice seedlings can still maintain a good growth trend.(3)In order to reduce the use of peat soil,a non-renewable resource in the soil covering cultivation of Agaricus bisporus,the effects of different proportions of combining biogas residue with peat soil and perlite into covering material on the yield and quality of Agaricus bisporus were studied.The results showed that compared with the control(75%peat soil+25%perlite),replacing 25%peat soil(25%biogas residue+50%peat soil+25%perlite)with biogas residue as the covering material had no significant effect on the yield of mushrooms,the nutrient composition of mushroom fruiting bodies did not change much,and the heavy metal content was also within the specified limits.It shows that it is feasible to replace part of the peat soil with biogas residue as the covering material for the cultivation of Agaricus bisporus,and has a good yield stabilization effect and safety.(4)Aerobic composting was carried out with different proportions of digestate,chicken manure and straw,and the changes of microbial community structure during the composting process were analyzed.The results showed that with the increase of the proportion of biogas residue in the composting system,the maximum temperature of compost increased and the cooling rate slowed down.After the composting,the p H value of each treatment was stable at about 7.20,the conductivity(EC)value was between 2400μS/cm～2800μS/cm,the carbon-nitrogen ratio was reduced to less than 15,and the T value were 0.53(chicken manure+straw,CK),0.62(chicken manure+straw+10%biogas residue,CSB10),0.58(chicken manure+straw+20%biogas residue,CSB20)and 0.62(chicken manure+straw+40%biogas residue,CSB40),respectively,indicating that the compost in each treatment has been decomposed.The microbial diversity in each compost treatment was sequenced and analyzed,and it was found that the addition of biogas residue could increase the species diversity of compost.At the phylum level,each treatment was mainly composed of Firmicute,Actinobacteriota,Proteobacteria,Chloroflexi,and Bacteroidota,and the bacterial community had obvious succession during the composting process.(5)The above compost and peat soil were prepared into a seedling substrate to explore the seedling breeding effect on cucumbers.The results showed that adding a certain proportion of compost could improve the seedling breeding effect and promote the growth and development of cucumber seedlings to a certain extent.Among them,the compost of CSB20 or CSB40 was mixed with peat soil at a volume ratio of 25%,and the cucumber seedling emergence reached 100%,and the morphological indicators of seedlings were improved to different degrees compared with the control(100%peat soil),and the absorption of K element by cucumber seedlings was improved. |
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