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

Abstract

Ghana produces several hundred million tons of agricultural and agro industrial residues annually. In the Kwaebibirem District in the Eastern Region of Ghana the processing of fruits of the major tree crops such as oil palm and cocoa together with the large cultivation of rice and maize generate high amounts of 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 of the quantities generated and their impact on the environment. The management of these residues is often a major problem for many oil producing countries. The purpose of this study was to characterize and quantify the major residues of 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 of questionnaires translated in the local languages. Samples of POME were taken from both large and small scale palm oil processing mills and characterised. Different combinations of the oil palm residues (EFB, MF, PKC and POME) were composted with and without cocoa pod husks (CH) or poultry waste (PW) to increase the K and P values of the compost. Rock phosphate (RP) was also used because composting was found to increase its solubility and to increase P content of compost where poultry waste was not available. Monitoring of the biochemical changes during composting was also carried out to ascertain the best indicator of maturity for 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 of Ghana Agricultural Research Station. The effects of the compost treatments on the growth and nutrient uptake of 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 (T11) and nine different compost treatments: T1(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) , T9 (EFB+PKC+POME) and TI0 (EFB+ Water) The findings by the author showed that about 33,025 metric tonnes of EFB and 73,229 m3 of POME were generated in the Kwaebibirem District. The pH values of MF and PKC ranged between 4.5 and 6.0 while that of the fresh POME and EFB were 4.6 and 9.0. Nitrogen content of the POME ranged between 1.30-1.80%. PKC showed highest phosphorus content (0.7%) while MF 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 pH (below 5), high Electrical Conductivity (31,300 /μS/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 of Ghana) for waste water quality standard guidelines for discharges into water bodies, and the Malaysian Standards for oil mill effluent for watercourse discharge. The POME was partly found to account for the high BOD (14.40mg/l), COD (166.70mg/l and low dissolved oxygen (0.93-1.23mg/l) of water bodies near the small scale oil palm processing Mills. The composting mixtures matured after 138 days of composting. Correlation of 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 of compost from agricultural and agro-industrial residues. The mixture of POME, PKC, cocoa pod husks, poultry waste or phosphate rock as composted material significantly improved the nutrient content of the compost .Percent nitrogen (N) ranged between 2% in T10 to about 5% in T3. Highest phosphorus (P) was recorded in T8 (4.4%) and potassium (K) in T4 (3.97%). Oil palm seedlings (OPRI and La Me) grown in compost treatments recorded higher number of leaves, leaf width, leaf length, seedling height, bole diameter, root volume and total dry matter yield than seedlings grown on inorganic fertilizer(T11) or imported organic fertilizer (T5 Flanamite). Uptake values of NPK by La Me seedlings were higher (920mg/plant,166 mg/plant, 740 mg/plant respectively) than by OPRI seedlings (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 of the managers of the mills and potential compost users (200 respondents) revealed that 92 to 96% of the respondents perceived compost as good and were ready to compost and use the compost for agricultural purposes. It is recommended therefore that composting could be considered as an effective method of managing agricultural and agro-industrial waste and in particular for the oil palm industry, it should be given utmost priority.