我國粗糠利用及粗糠爐之循環經濟分析

近期國內稻穀產量上升，連帶使礱穀副產物粗糠數量增加，不過以往能去化多數粗糠之雞舍用量卻有下降趨勢，其乃因加入益生菌可降低墊料更換頻率，如此去化受阻加上粗糠蓬鬆佔空間等特性，導致米廠存放空間不足，倉容負擔過重恐影響碾米作業。然而過往文獻多聚焦於粗糠之多元用途，未見以市場供需與循環經濟的角度切入分析，因此本研究欲了解目前我國粗糠市場運作概況，整合各類粗糠利用方式並建立農業剩餘資源之循環價值鏈，又深入分析其中最具節能減碳功效之烘乾稻穀燃料一用，探討粗糠爐在不同烘乾效率與電價漲幅下之經濟可行性，以及以粗糠取代燃油烘乾稻穀之益處。基於上述動機與目的，本研究針對我國稻米主要產區，即中南部之粗糠供給端、運銷端及需求端進行深度訪談，蒐集相關數據進行以粗糠爐烘乾稻穀之成本效益分析及敏感度分析，並彙整訪談內容，歸納出我國粗糠市場利用現況及粗糠爐相較於燃油機之優勢。受訪樣本共計15家粗糠通路業者，包含8家糧商、2家粗糠盤商及5家粗糠使用者。研究結果顯示，碾米副產物粗糠可形成一利用循環，其中以稻穀烘乾燃料之現地處理方式最佳，不僅沒有流向他處之中間成本，也可避免運銷過程產生碳排放。此外，烘乾量破萬噸的碾米業者通常會設置6套以上之粗糠爐，本研究以南部一大型碾米業者為例，計算6套粗糠爐24小時效能全開之總利潤為129.94萬元/日，平均每公斤可獲利1.80元。若加入烘乾效率及電價漲幅之變動，則隨電價上漲總利潤均會減少，不過只有上漲幅度在10%以上才會影響單位成本及利潤，而在電價不變的情況下，當粗糠爐烘乾效率降至原先的75%與50%，總利潤將隨之減少至96.28萬元/日與62.63萬元/日，每公斤獲利下降為1.78元與1.74元。由此可知，以粗糠爐烘乾稻穀具有經濟可行性，又將之與燃油機比較，乾燥成本從36萬元/日降低至2.88萬元/日，每天可節省33.12萬元燃料費用，且粗糠爐經集塵排灰處理後不會產生廢氣，每天可減少排放38.88公噸二氧化碳，相當於1.94公頃森林面積之碳匯，其燃燒餘燼之粗糠灰亦具固碳效果及循環再生價值，另尚有烘乾品質較佳、烘乾規模較大等優勢。不過粗糠市場受稻米烘乾期之燃料需求影響，價格會有季節性波動，故建議政府除了輔導糧商建置粗糠爐，亦可發展其他工業用途提高附加價值，如此不僅能緩解粗糠去化問題，也避免浪費資源、造成污染，兼具環境保護與經濟發展，有助於推動相關政策，調節粗糠供需之餘，亦加速我國農業淨零排放之進程。

關鍵字

粗糠；再利用；粗糠爐；循環經濟；農業淨零

並列摘要

Recent domestic rice production has increased, leading to an increase of rice husks, a by-product of rice milling. However, the demand for rice husks as bedding material for chicken coops has been declining due to the use of probiotics, which reduce the frequency of bedding replacement. On top of that, low bulk density of rice husk results in insufficient space to store rice husks in rice mills, putting a heavy burden on storage capacity and potentially affecting rice milling operations. Previous studies have mostly focused on the diverse uses of rice husks, but little attention has been given to analyses about the market supply-demand dynamics and circular economy. Therefore, this study aims to understand the current operation of the rice husk market in Taiwan, integrate various usage of rice husks, and establish a circular value chain for agricultural surplus resources. Furthermore, the study delves into the energy-saving and carbon-reducing benefits of using rice husks as fuel for drying rice, exploring the economic feasibility of rice husk furnaces under different drying efficiency and electricity price scenarios, along with the advantages of using rice husks instead of fuel oil for rice drying. To achieve the above objectives, this study conducted in-depth interviews with suppliers, distributors, and demanders of rice husks in the main rice-producing regions, the central and southern parts of Taiwan. Relevant data were collected to perform a cost-benefit analysis and sensitivity analysis for drying rice through rice husk furnaces. The study summarized the findings from the interviews, providing an overview of the current utilization of rice husks in the market and the advantages of rice husk furnaces compared to fuel oil burners. The study sample consisted of 15 rice husk industry players, including 8 grain merchants, 2 rice husk wholesalers, and 5 rice husk users. The results section indicate that rice husks can be effectively utilized in a sustainable loop, and it comes to the conclusion that to have on-site usage of making rice husks as fuel for drying rice is the most optimal method. This approach not only eliminates the intermediate cost of distribution but also avoids carbon emissions during transportation. In addition, rice mills that produce more than ten thousand tons of rice usually set up six or more rice husk furnaces. This research considers a large-scale rice mill in southern Taiwan as example. In this case, the total daily profit of operating six rice husk furnaces for 24 hours at full capacity is 1.2994 million NTD dollars, with an average profit of 1.80 NTD dollars per kilogram of rice. When considering variations in drying efficiency and electricity price, all of the total profits would decrease with the increase of electricity price, but only above 10% would affect unit costs and profits. Moreover, under constant electricity price, if the drying efficiency of rice husk furnaces decreased to 75% and 50%, the total daily profit would decrease to 962.8 thousand NTD dollars and 626.3 thousand NTD dollars, with profit per kilogram decreasing to 1.78 NTD dollars and 1.74 NTD dollars, respectively. Based on the above findings, using rice husks as fuel for drying rice is economically feasible. Compared to fuel oil burners, the daily drying cost of rice husk furnaces decreases significantly from 360 thousand NTD dollars to 28.8 thousand NTD dollars, resulting in daily saving of 331.2 thousand NTD dollars in fuel costs. Additionally, rice husk furnaces do not emit exhaust gas after dust collection and ash treatment, causing a reduction of 38.88 tons of carbon dioxide emissions per day, equivalent to a carbon sink of 1.94 hectares of forest. The ash residue from burning rice husks also has a contribution to carbon sequestration and can be recycled. Furthermore, the drying quality and scale of rice husk furnaces is better. However, the rice husk market is influenced by the demand for fuel during rice drying periods, leading to seasonal price fluctuations. Hence, it is recommended that the government not only support grain merchants in establishing rice husk furnaces but also explore other industrial usage to enhance added value. In this way, the problem about the disposal of rice husks, waste and pollution can be solved while promoting environmental protection and economic development. It will also contribute to advancing relevant policies, regulating rice husk supply and demand, and accelerating progress towards agricultural net-zero emissions in Taiwan.