The Long-term Storage And Biorefining Of Various Lignocellulosic Feedstocks In Multiple Areas And The Energy Application Of Heavy Metal Contaminated Feedstocks

This thesis focused on two important practical application issues,namely,the long-term storage of various lignocellulosic feedstocks in multiple areas and the energy-intensive application of heavy metal-contaminated biomass feedstocks.In the first place,lignocellulosic materials in China are widely distributed,with many varieties and rich output,which is extremely conducive to the energy application of biorefining.Before considering large-scale biorefinery applications,it is necessary to consider the strong dependence of multiple raw material supplies on the season.To guarantee the biorefinery plant can carry out stable energy production all year round,a critical problem must be solved,namely,the successful long-term storage of lignocellulose materials without microbial contamination.Besides,in order to avoid serious secondary pollution of heavy metals caused by direct disposal,it is particularly important to seek reasonable and proper methods to safely and effectively treat these heavy metal-contaminated biomass.Although the use of biorefining methods for the energy application of such contaminated biomass materials is an effective method close to this goal,it is even more important to prevent and control heavy metal secondary pollution while applying it.In order to solve the problems above,this study used a mature and excellent pretreatment technology developed by our laboratory,i.e.,dry acid pretreatment technology.And at the same time,we conducted a long-term storage test study of a wide variety of lignocellulose materials as well as the research on the whole-biomass biorefining of heavy metal contaminated biomass feedstocks.The main research methods and the important results finally obtained are summarized as follows:The first part of this thesis here mainly studies the replacement of long-term storage of several crop straws after dry acid pretreatment in multiple geographical environments of China.Firstly,to prevent the threat of mold during the long-term storage,we adopted a method of pretreatment first and then long-term storage.Secondly,in order to grasp the changes of the pretreated materials during long-term storage,a year-round follow-up test experiment was carried out on the spread of various pretreated feedstocks in different regions of China,mainly investigating the changes of physical and chemical properties,composition and enzymatic hydrolysis yield and ethanol fermentability of the pretreated.Finally,under the framework of decentralized supply,the relationship between the storage density of lignocellulosic feedstocks and the off-depot transportation cost was discussed.At last,the following results or goals were obtained.Firstly,the dry acid pretreated crop straws can achieve the one-year storage without microbial contamination in a variety of complex regional environments of China,so they have excellent resistance to mold.The performance also shows that this kind of method of pretreated first then storaged is reasonable.Secondly,after the dry acid pretreatment,the bulk density and tap density of raw straw materials are significantly improved,and the storage density of raw materials during storage is still positively rising.Therefore,such a property change helps to reduce the transportation cost of the feedstock supply process.Thirdly,the main inhibitor content of the dry acid pretreated feedstocks during storage is significantly reduced,thereby saving the time cost of subsequent biological detoxification.Fourth,the yield of enzymatic hydrolysis is significantly improved,and the overall ethanol fermentation performance is stable.The second part of this thesis takes rice biomass,which often occurs under the current heavy metal pollution in the soil,as the research object,and mainly studies the current biomass refining method based on dry acid pretreatment technology.The rice straw and rice grain of heavy metal contaminated rice are contaminated biomass with potentially secondary pollution capability,and can be used for energy application.If not handled properly,it is very easy to cause serious consequences.The dry biorefining process based on dry acid pretreatment technology can be realized first with totally enclosed energy utilization of heavy metal contaminated rice straw,but contaminated rice does not have a good use method.If it is used for ethanol fermentation alone,it will inevitably produce a large amount of heavy metal contaminated distillers that can be illegally used as animal feed,and resulting in serious heavy metal secondary pollution.In order to avoid separate fermentation of rice,we have tried a method of whole-biomass biorefining,i.e.,preparing contaminated rice into hydrolysate and integrating it into the ethanol fermentation process of rice straw in the form of supplementary raw materials to realize a form of whole-biomass fermentation,thus avoid the occurrence of heavy metal contamination.In the end,it not only achieved an ideal ethanol index(56.3 g/L),realized energy utilization,but also successfully achieved full-enclosed treatment of contaminated rice biomass without secondary pollution,and realized the enrichment of heavy metals.In summary,dry-acid pretreatment technology is of great significance for the long-term storage of a wide variety of lignocellulosic feedstocks and the fully enclosed energy-intensive application of heavy metal-pollution raw materials.The application of dry acid pretreatment technology can not only successfully solve the problem of long-term storage of crop straw and other lignocellulosic feedstocks,but also create favorable conditions for the whole-biomass utilization of heavy metal contaminated rice.Therefore,this research has made certain contributions to the future supply of raw materials for biorefinery plants and the safe and effective treatment of biomass contaminated by heavy metals.