Co-composting of Green Waste and Food Waste by Lab-scale and Field-scale Composting Reactors
|關鍵字:||綠色廢棄物;食品廢棄物;混合堆肥;戶外堆肥反應槽;Food waste;Green waste;Co-composting;Field-scale composting reactor|
實驗結果顯示，採用槽式堆肥之食品廢棄物及綠色廢棄物之混合堆肥能在12天內被分解，高於過去文獻之堆肥反應速率且達到相當高的去除效率 (>30%)。碳氮比及含水率為堆肥實驗之重要參數，藉由中央合成設計法調整碳氮比及含水率並利用反應曲面法可得到最佳操作條件。中央合成設計法及反應曲面法所得之結果顯示，食品廢棄物及綠色廢棄物之混合堆肥之最佳含水率為60%；碳氮比在本研究中並非顯著之因子，但碳氮比表示綠色廢棄物及食品廢棄物之比例，進而影響堆肥物種之孔隙率及氧氣傳輸效率，因此，含水率及碳氮比之交互作用之影響為顯著的。此外，總揮發性固體物之去除率符合二階模型，其R2 高於95％。
Both food and green wastes are the most organic sources in municipal solid wastes, which can be reused as soil amendments or organic fertilizer for land application after proper treatment. Land filling/dumping and incineration are the most common ways to treat these organic wastes. Several dumpsites have been closed down in recent years due to the confined land availability in various countries including Taiwan. Furthermore, the high moisture content of organic waste reduces the incineration efficiency, and damages the incinerator as well as the process performance, thus resulting in the secondary pollution. Therefore, composting has become more popular due to its low energy cost, low technology demand, as well as the reusability of the end product. The main objectives of this study are to convert green waste and food waste into stable reusable products using lab-scale composting at optimal operating conditions and to design a field-scale reactor to mimic these conditions. The results showed that food waste and green waste can be decomposed in 12 days with in-vessel composting, a shorter composting time than in previously published literature, and produced better total volatile solids (TVS) reduction ratio (>30%). A central composite design and response surface method were applied to obtain optimal operating conditions at different design moisture contents and carbon to nitrogen ratios. The central composite design and response surface method results indicated that the optimal moisture content for co-composting of food waste and green waste was 60%. Whereas the change in moisture content was a highly significant factor, the central composite design and response surface method results indicated that the carbon to nitrogen ratio was not. The TVS reduction ratio was modeled by a second-order equation with a correlation R2 value higher than 95%. A field-scale composting reactor was designed without an agitator or aeration pump to save on electrical power use. The performance of the field-scale reactor yielded better results than the lab-scale reactor, producing a higher temperature and TVS reduction ratio. The better performance of the field-scale reactor is due to the increase in agitation efficiency. The results indicated that the agitation type is more important than agitation time when designing a composting reactor. The samples collected from the field scale reactor have nearly reached the value of standard germination index of radish seed, which shows that compost produced in this study can be applied as soil amendment.