| Summary: | 碩士 === 國立高雄海洋科技大學 === 海洋環境工程研究所 === 101 === Rice is both the main crop and staple in our country. According to the statistics made by the Agriculture and Food Agency, it can be inferred that, due to the planting of rice, the annual average amount of straw is 1.86 million tons in the past decade. Thus, the amount of discarded straw is quite large. Overall speaking, every method of dealing with the discarded straw bears its own advantages and disadvantages; so far, there hasn’t been any ideal way about it. However, it’s more environmentally-friendly to conduct it through composting, namely, a process of proper composting fermentation, which will not only deal with the crop waste, but also lessen its impact on the environment. If the problem about the fiber in the straw can be solved, which makes the straw uneasy to ferment and decomposed, and, thus, the composting take a long time to be done, we can solve the problem of the consumption of time in the composting of straw. This technique can also make the straw resources, offering a both environmentally-friendly and recycling method.
To solve the problem of the straw fiber’s being hard to be decomposed, this research plans to make an experiment in two stages by using straws as the main material. 1. Do the preliminary treatment of straws by soaking. The liquid for soaking are respectively as following: (1) neutral soaking liquid: tap-water, waste water for rice washing and liquid fertilizer; (2) acid soaking liquid: oozing water from the food waster and iced acetic acid; (3) weak alkaline soaking liquid: cattle’s excrement, pigs’ excrement, chickens’ excrement, urine and limewater; (4) strong alkaline soaking liquid: sodium hydroxide and black liquor. There are twelve kinds of soaking liquid in total and the preliminary treatment is conducted in 264 hours. 2. Do the composting by applying the result of the above treatment to the composting, exploring the differences between directly using the soaked straws in the composting and using the soaked straws with additives in the composting.
The research result shows that: 1. preliminary treatment (from monitoring the parameters): (1) the change of moisture content: the moisture content of the straws rapidly increases after they’ve been soaked for 24 hours; the moisture content of the straws soaked in the neutral, acid and weak alkaline liquid reaches 75%; the one of the straws soaked in the strong alkaline liquid reaches about 60% to 70%. When the soaking continues, the moisture content maintain stable; (2) the change of ph value: there is a positive correlation between the straws and the ph value of the soaking liquid; (3) the change of the lignin content: the more alkaline the soaking liquid is, the more efficient the removing of lignin is; (4) the change of the straw’s loading: the change is fast at first, which is probably related to the straw’s absorbing of water, and then the change goes similarly with the one of lignin content; (5) with making a whole contrast among all the preliminary treatment statistics, we can get the ranking of the soaking liquid from high to low based on its destructive level to the straw’s structure: strong alkaline soaking liquid > weak alkaline soaking liquid > acid and neutral soaking liquid; however, considering the high cost of strong alkaline soaking liquid and safety concern, it’s not involved in the compost experiment. Thus, the liquid used in the preliminary treatment will be the less effective one ─ chicken’s excrement and limewater. Also, regarding the rich microflora of the liquid fertilizer, it’s included. With the tap water as the control group, there are totally four soaking liquid in the preliminary treatment, which is respectively used in the composting experiment without any additive. With tap water as the soaking liquid first, three other composting experiments respectively added with compost, food waster and food waster and chicken’s excrement are also conducted. 2. The change of parameters during the composting: (1) the high temperature period of compost with additives is longer than the one without additives. The temperature difference can reach more than 20℃; (2) the moisture content decrease with the increase of composting temperature, but it can largely controlled between 70℃ to 85℃; (3) the ph value will rise from the relative acid (pH=6-7) to 8.5 to 9.5, and then slowly falls down, maintaining 8.0 to 8.3 in the end; (4) EC goes similarly with pH, rising from the relative low point, next falling down, maintaining stable in the end; (5) the change of the lignin content in the compost with additives is better than the one without additives. The removing efficiency of the former is 5% better than the latter; (6) after 60 days of composting, except that the C/N of the compost with liquid fertilizer is 37, others all falls down to11-20, the standard of compost maturity.
In all, the results show that this research of dealing with straws as resources is capable and bears the advantages of simple manufacturing, low failure, low contamination and high quality composting. However, the mail goal of this research has reached; as for the space for improvement of the composting products, it can serve as a way for the next research.
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