Study On The Life Cycle Assessment Of Active Dry Yeast Production

Active dry yeast plays a very important role in the lives of residents in China.It has many advantages,such as stable performance and easy transportation,and is widely used in the field of fermented pasta processing and winemaking.However,the production of active dry yeast causes serious environmental pollution,which has aroused public concern.Therefore,the yeast industry should take more effective measures for environmental impact.Life cycle assessment(LCA),as an effective environmental assessment method,can scientifically and comprehensively evaluate the environmental load generated during the entire life cycle of yeast production.Hence,this study aims to assess the impact of yeast production on the environment from the perspective of a full life cycle.A yeast industry LCA evaluation tool was constructed by establishing an active dry yeast production list,production process,and collecting inventory data to provide guidance for green production.The yeast production list includes the names of raw and auxiliary materials,consumption,and related emission types.Based on the production list,a flow chart of yeast production LCA was established to determine the types of environmental impacts related to yeast production,including global warming of yeast production(GWP),primary energy consumption(PED),eutrophication(EP),acidification(AP),water resource consumption(WU),absorbable inorganics(RI),and finally to built the yeast industry LCA evaluation tool to establish and improve the yeast industry database.This study establishes a production life cycle list of high-sugar-tolerant active dry yeast and sugar-free active dry yeast products.The list lists each production model,as well as the names,units,quantities,and upstream data sources of materials related to consumption and emissions.Taking dry yeast with the high sugar resistance activity as an example,the established LCA evaluation tool is used to identify the main environmental impact value and proportions of each process of yeast production:the key process affecting the environment in GWP is the fermentation process,followed by the granulation and drying process;The key process that affects the environment in PED is fermentation,followed by granulation and drying;the key process that EP affects the environment is fermentation,followed by raw material pretreatment;the key process that AP affects the environment is fermentation,followed by granulation and drying process;the key process that WU affects the environment is the fermentation process,followed by separation and washing;the key process that the absorbable inorganics(RI)affects the environment is the fermentation process,followed by granulation and drying.Overall,it can be seen that in yeast production,the degree of environmental impact from high to low is as follows:fermentation,granulation and drying,separation and washing,and raw material pretreatment process.Based on the inventory data of the two active dry yeasts,six types of molasses(Hainan-Sugarcane,Guangxi-Sugarcane,Yunnan-Sugarcane,Xinjiang-Beet,Heilongjiang-Beet,Inner Mongolia-Beet)and 4 different production processes were selected to synthesize ammonia(often pressure intermittent conversion method,fixed-bed intermittent gasification method,steam reforming method/continuous pressurization method,and coal water slurry pressurized gasification method)as the research object.Based on the above six environmental impact values as indicators,the constructed LCA evaluation tool was used to study the source selection of high-tolerance active dry yeast and low-sugar active dry yeast.It was determined that ammonia synthesis from Inner Mongolia-Beet molasses,steam conversion method/continuous pressurization method could reduce the environmental impact value of yeast production.