Accounting carbon emission in the layer breeding industry of North China

North China has been one of the main regions in laying hens breeding. There is a high demand to standardize the carbon emission accounting of the laying hen breeding industry at present, in order to formulate carbon emission reduction technologies and policies in the carbon emission inventory of the animal husbandry industry. Particularly, carbon emissions are ever-increasing, as the laying hen industry is developing rapidly. However, it is still lacking in the carbon emissions of the whole industry chain in the layer breeding. This study aims to improve the carbon emission factors of the layer breeding industry in North China. A carbon emission accounting was also implemented for the layer breeding industry, according to the IPCC national greenhouse gas inventory guidelines. The mixed life cycle was then adopted to assess. The data was collected from the field research and meta-analysis data. 362-layer farms in Hebei Province were taken as an example. The benefits of carbon emission reduction were calculated from the whole chain (feed planting and processing, layer feeding, and manure management). Furthermore, the carbon emission sources were determined for the whole industry chain in the layer breeding. The results showed that the annual carbon emissions (in terms of carbon dioxide equivalent) per layer in the small, medium and large-scale farms were 25.6, 24.4 and 23.0 kg, respectively. The main emission sources were feed production (56.0%), enteric fermentation of laying hens (9.0%), egg packaging (9.0%), and manure storage and treatment (5.0%). The precise feeding was obtained to improve the manure cleaning. The optimal manure treatment also reduced the carbon emissions. There were also the traditional modes of laying hen breeding and extensive management. For example, the amount of feed varied by 5% to 10% among different farmers. A comparison was performed on the farms with the different size scales. Some measures were taken to avoid wasting resources. The large amount of carbon emission was needed to improve during the laying hen breeding. According to the survey, a series of measures were proposed to reduce carbon emissions, including specific ingredients in the feed, optimal feed structure, and better waste disposal. The laying hen breeding industry should be transformed in the direction of modernization, scale, standardization and automation. The precise feeding can be expected to improve feed utilization and energy saving. The level of waste treatment can also be promoted to reduce greenhouse gas emissions for the green and coordinated development of the laying hen industry. The carbon emission also accounted for the carbon emissions in the whole life cycle of layer breeding. The finding can provide a strong reference to analyze the carbon emission of layer breeding in different scale farms and emission sources. Carbon emission reduction measures are also suitable for different farms. Data support can also be offered to assess the carbon emissions intensity of the layer breeding industry.