274 Fig. 2 Progressive fragmentation of polysaccharides in MC fermentors (circles), and after, MC-treated materials were amended in soil (triangles). The progressive decrease in the EPF index values indicates ongoing hydrolysis and breakdown of WIAS polysaccharides into smaller size fragments. Each data point in the amended soil is a single determination taken at the time shown in the plot. Error bars are ±2 SD of triplicate assays Appl Biochem Biotechnol (2011) 165:270–278 sufficient O2 (~1–2%) retained in the headspace of the fermentors. These conditions are known to inhibit the activity of methanogens [23–25]. The pH of compost tea drawn from the MC fermentor containing leaf feedstock began at ~5.5, bottomed out at 3.69 by the 10th day, and over the next 20 days remained remarkably stable (i.e., dropped by only an additional 0.16 pH units). VOAs (principally acetic, propanoic, butyric, and to a lesser extent isovaleric and valeric acid) and alcohols (principally ethanol, and in lesser amounts propanol) reached steady states within the first ~10 days (data not shown). Similar results regarding pH, the EPF, VOAs, and alcohols were seen using food scrap in place of oak leaves in 20- and 210-L capacity fermentors. In 210-L fermentors, the average pH of the compost tea derived from MC food scraps was remarkably similar to that seen in tea derived from MC leaves and consistent at 3.65 ± 0.06 (n = 6, ±1 SD) by ~7 days after composting was started. Glucose equivalents (based on the PSA assay) averaged 9.2 ± 1.8 mg ml−1 (n = 6, ±1 SD), and the ethanol content was 0.80 ± 0.14% w/v (n = 6, ±1 SD). Approximately 10–15 L of tea was produced per week by each 210-L fermentor containing food scrap. About 2% of the initial C was recovered in the form of glucose, alcohols, and VOAs. Processed residue from 210-L fermentors was amended into soil to a depth of ~5–20 cm in ~100-m2 swaths at varying loads ranging from 10 to 70 kg m−2. Tea was set aside for further studies and testing since it appeared too acidic (~3.6 pH) and rich in by-products (VOAs and alcohols) to be applied directly to the soil. The pH of soil amended with processed residue showed a biphasic shift in pH relative to the date of its amendment in soil, starting slightly higher than that of the tea (~4.5), and shifting into the neutral pH range within 10 days, and thereafter slowly climbing upward toward that of control soil over a period of approximately 5 months (Fig. 3). Control (unamended) soil had a pH in the range 7.5–8.0. The transient and rapid upward shift in soil pH seen during the first 10 days after amendment of processed food scrap into soil was confirmed by re-examining the pH of three sites showing an initial low soil pH. Follow-up testing made on drawing a second set of soil samples from the same sites 2 weeks later showed that they had shifted upward in pH into the neutral range (>6.5). The half-life of the MC food scrap amended in soil was about 100–110 days (Fig. 4). Changes in the EPF index correlated with changes in the residual polysaccharide content (Fig. 4). There was however an upper limit (6–9%) in polysaccharide content achieved with progressive increasing loads of processed food scrap amended into the soil (Fig. 5). The