Incinerated distillery spent wash technology has been developed under zero liquid discharge (ZLD) process for the sustainable development of the sugar and alcohol production industry. The ash generated by the incineration of distillery spent wash has been reported as a fertilizer source due to its high potash content, but its environmental impact is unknown because it is applied indiscriminately to agricultural soil. However, the spent wash after incineration retains a high pH (9.5) and various salts and heavy metals, including iron, nickel, and chromium (ranging from 2335.21 to 2363.00 mg/kg). In addition, a recent study has also revealed the presence of 2,4-dimethylbenzene and dichloroacetic acid as toxic compounds and suspected carcinogens. A recent study has pointed out that, for their toxic effect on seed germination and plant growth, the high pH, along with multi-metal contents, may impose adverse effects on soil microflora. Therefore, comprehensive information regarding the latest method for the bioconversion of incinerated spent wash ash into organic manure for sustainable agriculture is essential for maintaining soil health; this will meet the Sustainable Development Goal (SDG) goal for responsible consumption and production. The proper balance among bacteria, pollutants, and environmental conditions governs the bioconversion of complex waste. Moreover, the balance between carbon and nitrogen ratios, along with other nutrients, is a prerequisite for microbial growth. Therefore, the present chapter provides comprehensive information on the organic and inorganic composition of incinerated spent wash ash and the optimum conditions required for bio-composting and valorization for sustainable agriculture.