Life Cycle Environmental Impact Of Typical Amino Acid Products

China is a large country of amino acid production and consumption,with large consumption of resources and energy in the production process.It is urgent to promote the green and low-carbon development of the industry.This study used life cycle assessment method,combined with water footprint,life cycle cost analysis and water energy nexus methods to study the environmental impact of typical amino acid product production system.Started with maize,an important raw material of amino acid products,this research collected the planting data of the main maize supply areas of amino acid enterprises in China,calculated the environmental impact under the monoculture system in Inner Mongolia,Heilongjiang and the rotation system in Shandong,and compared it with the background data of the database.At the same time,aimed at the problem of large water consumption of Maize Irrigation in China,the water footprint was calculated.Then selected the appropriate real process of maize planting to study the LCA of amino acid products.According to the progress of cleaner production level in China’s monosodium glutamate（MSG）industry in recent ten years,four typical scenarios of MSG production from 2008 to 2019 were established,and carried out the LCA study from"cradle to gate".The environmental impacts including primary energy demand（PED）,resource depletion-water use（WU）,global warming potential（GWP）,acidification potential（AP）and eutrophication potential（EP）were calculated for normalization and weighting assessment,and analyzed sensitivity and uncertainty of the results.For lysine products,two major lysine salts（98.5%lysine hydrochloride and 70%lysine sulfate）in the market were selected according to the difference of lysine purity,and the six environmental impacts of PED,WU,GWP,AP,EP and ecotoxicity（ET）were calculated.According to the sensitivity and uncertainty analysis,the improvement scheme of cogeneration technology was put forward,and analyzed the life cycle cost of different technology.Finally,studied the water-energy nexus of wastewater treatment process in amino acid industry,and analyzed the key stages and factors affecting energy consumption.The LCA results showed that the environmental impact value of maize planting in China was quite different from that in the database,and the WU gap was more than 250times.The scenarios of improving irrigation and fertilization methods can reduce GWP,PED,EP,AP and WU by 30.24%,21.27%,11.16%,4.76%and 3.03%respectively.Applying organic fertilizer instead of mineral fertilizer can reduce PED,WU and ET by40%～50%.The water footprint of maize planting in Heilongjiang was 0.362m³/kg,in which the gray water footprint accounts for the largest proportion,which was mainly related to the application amount of nitrogen fertilizer in the field and the yield of maize.On the basis of ensuring the yield of maize,the application amount of chemical fertilizer should be reduced as much as possible.With the improvement of cleaner production level,the environmental impact of MSG products has been continuously reduced.The PED,GWP,WU,AP and EP of 1t monosodium glutamate produced in 2019 are 52800 MJ,169000 kg,4590 kg CO₂eq,42.1 kg SO₂eq and 6.35 kg PO₄^3-eq.Sensitivity and uncertainty analysis showed that steam,irrigation water and ammonia volatilization were the key substances in the process of maize planting.It is proposed to use natural gas and biomass gas instead of coal for steam production.Biomass gas has lower PED,WU and GWP.The PED,GWP,WU,AP,EP and ET of 98.5%lysine hydrochloride are 73800 MJ,6050 kg CO₂eq,666000 kg,51.9 kg SO₂eq,7.72 kg PO₄^3-eq and 72.7 CTUe respectively.70%lysine sulfate is lower for the selected environmental impact indicators due to its low lysine purity and low consumption of raw materials and energy.Sensitivity and uncertainty analysis shows that in addition to steam,irrigation water and ammonia volatilization,ammonium sulfate and liquid ammonia are also key lists.Two technical schemes of lysine co production are proposed.The reuse of ammonium sulfate instead of some liquid ammonia can reduce the environmental impact of producing 1t 98.5%lysine hydrochloride by about 20%.At the same time,the life cycle cost analysis results show that the economic benefit of the joint production scheme is only 239.12 RMB lower than the unit yield,which has the best environmental and economic benefits.The water energy nexus analysis of amino acid wastewater treatment process showed that the Pearson correlation coefficient between influent carbon nitrogen ratio and energy consumption was-0.873,showing a significant negative correlation,and the Pearson correlation coefficient between ammonia nitrogen volume load and energy consumption was 0.939,showing a significant positive correlation.It shows that reducing the concentration of ammonia nitrogen in influent becomes the key to the development of low-carbon in wastewater treatment process.We should vigorously promote the best available technology in amino acid industry and improve the utilization rate of nitrogen source,which can not only reduce the environmental impact of product life cycle,but also be of great significance to the low-carbon development of wastewater treatment process.The research results will provide theoretical support for the green and low-carbon transformation of amino acid industry.