The experiments at optimum conditions (pH 5.5, 41◦C) in batch 4 and 5 were carried out to 24 h with time having a varied, yet minor, effect on the final lactate concentration. Batch 4 lactate concentrations increased from 37.0 to 38.1 g L−1 and batch 5 decreased from 47.3 to 44.5 g L−1 between 16 and 24 h respectively. This optimum is supported by the depletion of carbohydrates; at 24 h an 80% reduction of carbohydrates was observed (discussed in Section 3.3). Carbohydrates were evaluated in monomeric form after acid hydrolysis, and the measurement represents the potential carbohydrates available for conversion to lactate. However, a fraction of the carbohydrates measured are recalcitrant, including the cellulose fiber from toilet paper in the primary sludge. Due to the acid hydrolysis, the cellulose fraction was registered within the total glucose the same as readily degradable polysaccharides, despite the fiber not being available for biological conversion to lactate within the short duration of the digestion. As a result the measurement of 80% carbohydrate reduction under represents the conversion of food waste to lactate and further supports the optimal as less than 24 h.