Evaluation of Agricultural and Agro- industrial Residues for Composting for Agricultural Use in Ghana

ABSTRACT Ghana produces several hundred million tons o f agricultural and agro industrial residues annually. In the Kwaebibirem District in the Eastern Region o f Ghana the processing o f fruits o f the major tree crops such as oil palm and cocoa together with the large cultivation o f rice and maize generate high amounts o f agricultural and agro industrial residues. Oil palm residues comprising empty fruit bunches (EFB), palm oil mill effluent (POME),mesocarp fibre(MF) and palm kernel cake (PKC) are significant among the agricultural and agro industrial residues, because o f the quantities generated and their impact on the environment. The management o f these residues is often a major problem fo r many oil producing countries. The purpose o f this study was to characterize and quantify the major residues o f oil palm processing, determine their impact on the environment, their potential uses in agriculture and to recommend appropriate management methods. To achieve these objectives surveys were conducted through interviews and administration o f questionnaires translated in the local languages. Samples o f POME were taken from both large and small scale palm oil processing mills and characterised. Different combinations o f the oil palm residues (EFB, MF, PKC and POME) were composted with and without cocoa p od husks (CH) or poultry waste (PW) to increase the K and P values o f the compost. Rock phosphate (RP) was also used because composting was found to increase its solubility and to increase P content o f compost where poultry waste was not available. Monitoring o f the biochemical changes during composting was also carried out to ascertain the best indicator o f maturity fo r such compost mixtures. The parameters monitored during composting included: pH, temperature, carbon dioxide evolution, C/N, ammonium and nitrate nitrogen concentration and seed germination index. The resultant compost treatments were tested over eight months in a field experiment (2003-2004)at the University o f Ghana Agricultural Research Station. The effects o f the compost treatments on the growth and nutrient uptake o f two different oil palm varieties (OPRI and La Me seedlings) were evaluated at the pre-nursery and the nursery stages using a Randomized Complete Block Design (RCBD). The treatments were Flanamite (imported organic fertilizer, T5), 15:15:15NPK (Tji) and nine different compost treatments: Ti(EFB+POME), T2 (EFB +POME+MF), T3 (EFB + PKC +Water), T4 (EFB+PKC+CH+ POME), T6(EFB + PKC + CH + PW + Water), T7 (EFB+PKC+CH+PW+POME), T8 (EFB+EFB+PKC+CH+RP+POME) , t 9 (EFB+PKC+POME) and TI0 (EFB+ Water) The findings by the author showed that about 33,025 metric tonnes o f EFB and 73,229 m3 o f POME were generated in the Kwaebibirem District. The p H values o f M F and PKC ranged between 4.5 and 6.0 while that o f the fresh POME and EFB were 4.6 and 9.0. Nitrogen content o f the POME ranged between 1.30-1.80%. PKC showed highest phosphorus content (0.7%) while M F recorded the least (0.20%). Potassium content was highest in EFB (2.10%) and lowest in POME (0.06%). Whereas the large scale oil palm processing mills treated their POME through anaerobic digestion, the small and medium scale oil palm processing Mills did not. The untreated POME which is usually discharged into the environment had low p H (below 5), high Electrical Conductivity ( 31,300 /uS/cm,), high Total Dissolved Solids, TDS (181,200mg/l), Chemical Oxygen Demand, COD(133,760mg/l ), Biological Oxygen Demand, BOD (44,566mg/l) and oil content (560,250mg/l) higher than critical values supplied in the Environmental Protection Agency (EPA o f Ghana) fo r waste water quality standard guidelines fo r discharges into water bodies, and the Malaysian Standards fo r oil mill effluent fo r watercourse discharge. The POME was partly found to account fo r the high BOD (14.40mg/l), COD (166.70mg/land low dissolved oxygen (0.93-1.23mg/l) o f water bodies near the small scale oil palm processing Mills. The composting mixtures matured after 138 days o f composting. Correlation o f maturity parameters with germination index showed that alkaline pH, CO2 evolution, temperature and nitrates were found to correlate best with percent tomato seed germination test in determining the maturity o f compost from agricultural and agro-industrial residues. The mixture o f POME, PKC, cocoa pod husks, poultry waste or phosphate rock as composted material significantly improved the nutrient content o f the compost .Percent nitrogen(N) ranged between 2% in Tioto about 5% in 7j. Highest phosphorus (P) was recorded in Ts (4.4%) and potassium (K) in T4 (3.97%). Oil palm seedlings (OPRI and La Me ) grown in compost treatments recorded higher number o f leaves, leaf width, leaf length, seedling height, bole diameter, root volume and total dry matter yield than seedlings grown on inorganic fertilizer(Tu) or imported organic fertilizer (T^Flanamite). Uptake values o f NPK by La Me seedlings were higher (920mg/plant,166 mg/plant, 740 mg/plant respectively) than by OPRIseedlings (836.76 mg/plant, 95.83 mg/plant, 489.97 mg/plant respectively ) in the same compost treatments. The correlations between dry matter yield (DMY) and nutrient uptake in both OPRI and La Me seedlings were strong and positive (r = 0.9 and 0.96 respectively). Surveys conducted with questionnaires and interviews on the perception and willingness o f the managers o f the mills and potential compost users (200 respondents) revealed that 92 to 96% o f the respondents perceived compost as good and were ready to compost and use the compost fo r agricultural purposes. It is recommended therefore that composting could be considered as an effective method o f managing agricultural and agro-industrial waste and in particular fo r the oil palm industry, it should be given utmost priority.