## 1 Introduction  
The excess use of nitrogen (N) fertilizers in agriculture is increasing rapidly for food and bioenergy production due to the world's fast-growing population. To protect the environment, many wastes such as agricultural manure and crop residues can be recycled in a better way than they are currently managed. According to an estimate, 2.6 million tons per day of municipal solid waste is produced globally, and the amount may reach up to 4.5 million tons per day by 2050, International Solid Waste Association (ISWA) [1]. Composting is a useful method to reuse wastes such as manure [2], while the vermicomposting technique is more beneficial compared to composting as it provides for improved bioavailability of all macro- and micronutrients [3]. Vermicompost is an organic fertilizer made up of waste material processed in the guts of earthworms, which contain microbes and enzymes that ingest and absorb the organic waste [4]. Vermicompost is an organic amendment rich in nutrients and active in the microbiological perspective as a result of the microbiological breakdown of organic matter [5]. Though some of the inorganic plant nutrients are already present in the soil, they are supplemented by gradual release during organic matter mineralization, thus creating a slow but constant source of nutrients. Vermicompost has been regarded as an ecofriendly alternative for the recycling of organic solid waste. It also acts as a soil conditioner that helps plant growth [6]. Aerobic composting has gained attention for remarkable recycling of organic solid waste [7], with high organic content and low cost [8], great nutritional capacity [9] of municipal solid waste, profitable application of the end product [10], and less ecological damage than incineration and landfilling if appropriately handled. _Eisenia fetida_ is one of the most important family members of Lumbricidae that can frequently be used for vermicomposting [11]. [PERSON] and [PERSON] [12] also studied a dominant group of Lumbricidae from the soil fauna in purple soil, which was considered the most useful species for vermicomposting. Biochar can also be utilized as a soil nutrient enrichment for improved production of crops and as a stimulator of composting substances that can further be used in horticulture and environmental purposes, for example, as a combination with manure for nutrient recycling [13]. Furthermore, sufficient information is not available for vermicompost production using biochar as an alternative to manure. Extensive diversity of organic litter consisting of animal dung, leftovers from industries, sewage muck, and agricultural residues were widely recycled to prepare vermicast using earthworm species [14; 15]. Manure could play an important role in the cycling process to recover nutrients and part of energy sources [16]. Therefore, improper management may also cause environmental pollution. The crop residues from the fields are not rich in nitrogen and require supplementary material to fulfill soil microorganisms' nutrient requirements; hence, organic substrates are also provided to the soil during vermicomposting [17]. Among crops, rapeseed is considered rich in protein. Its leftovers after processing can be used as a vermicompost substrate [18]. Rapeseed is the largest cultivated crop in China and constitutes 20% of the world's production [19]. Wheat straw and rapeseed are important field crops cultivated in the winter season, producing large amounts of agricultural waste in upland areas of the Sichuan Basin. The interaction of earthworms with wheat straw and rapeseed has been studied during vermicomposting through different manure [20; 21]. However, there is still a knowledge gap for the field-scale study to recover nutrients and emission of gases (NH\({}_{3}\) volatilization and GHGs) during nutrient recovery from agricultural organic waste. Ammonia emissions produce adverse effects in the atmosphere by spreading atmospheric particulates and eutrophication and reducing nitrogen (N) efficiency [22].