Sustainable production of biochar-enriched organic fertilisers from sugar industry waste: Enhancing soil fertility and crop growth

Abstract

Sri Lanka’s sugar industry generates significant organic waste, including bagasse, ash, spent wash, and cane tops, much of which is underutilised or improperly discarded, posing environmental challenges. Concurrently, the nation grapples with soil degradation, fertiliser shortages, and declining agricultural productivity, creating a pressing need for sustainable alternatives to conventional fertilisers. This study investigates the conversion of these sugar industry wastes into paddy husk biochar-enriched organic fertilisers and evaluates their effectiveness on corn (Zea mays) growth. A 45-day greenhouse experiment was conducted to assess six different fertiliser formulations (T1-T6), each with three replicates, alongside a commercial organic fertiliser control (T7) and an unfertilised soil control (T8). The treatments varied in their composition of sugar industry wastes: T1 (100% bagasse), T2 (50% bagasse, 50% ash), T3 (50% bagasse, 25% ash, 25% spent wash), T4 (50% bagasse, 50% cane top), T5 (50% bagasse, 16% ash, 16% spent wash, 16% cane top), and T6 (50% bagasse, 50% spent wash). Each treatment was mixed 50:50 with soil and biochar in polybags to ensure a uniform growing medium under controlled conditions. Biochar was produced at 420 ◦C with a residence time of 40 minutes in a batch-type reactor. Plant growth was monitored by measuring height, girth, leaf count, and dry matter content. Data was analysed using repeated measures ANOVA in SPSS 26. The results demonstrated that the T5 formulation significantly outperformed all other treatments (p < 0.05) across all measured parameters, remarkably exceeding the commercial control. In contrast, treatments T1, T2, and T6 showed the lowest growth rates and were statistically nonsignificant compared to the control (p > 0.05). T3 and T4 promoted higher growth than the poorer-performing treatments but were not as effective as T5. The study concludes that the T5 mixture, comprising 50% bagasse with balanced proportions of ash, spent wash, and cane top, is the optimal formulation. This finding highlights the potential of repurposing sugar industry waste into high-value biochar fertilisers to enhance soil fertility, boost corn productivity, and advance sustainable waste management in alignment with Sri Lanka’s agricultural initiatives.