**5. Implications of findings for policy and practice**

The characteristics of the different wastewater streams and the current waste management practices at the small-scale mills in Ghana suggest the need to adopt appropriate and sustainable management practices.

#### **5.1 Enforcement of environmental regulations**

Wastewater is currently disposed on the bare ground without any form of treatment. Considering the characteristics and wastewater disposal practices, particular attention should be paid to the small-scale processing mills which dominate the palm oil production sector. In terms of policy, Regulation 1 of the Environmental Assessment Regulations, 1999 (LI 1652) [44] requires specific undertakings including oil and fats processing to register with and obtain environmental permit from the Ghana EPA prior to the commencement of the undertaking. In addition, existing undertakings, where EPA considers to have or is likely to have adverse effect on the environment or public health, are required to register with and obtain environmental permit in respect of the undertaking. Therefore, palm oil processing mills (including small-scale mills) are required to register with and obtain an environmental permit. However, small-scale processing mills belong to the informal sector where compliance to legal requirements is relatively weaker [22, 23]. The Ghana EPA, which is responsible for ensuring environmental compliance in Ghana, should extend enforcement of the Ghana Environmental Protection Requirements for Effluent Discharge to the small-scale (cottage) industries to ensure compliance. The government of Ghana, acting through the relevant agencies and the Artisanal Palm Oil Millers and Outgrowers Association, should provide technical support on sustainable waste management to the small-scale processing mills.

#### **5.2 Selection of appropriate management solutions**

Many technologies have been tested and applied to successfully treat palm oil mill wastewater mostly in Asia. Detailed description of different treatment methods can be found in the works by Liew, Kassim [45], Iskandar, Baharum [46] and Ohimain and Izah [47]. However, the selection of management solutions particularly for resource constrained environments such as what pertains in small towns and villages in Ghana where small-scale mills are located, must follow the principle of 'appropriate' technology. More importantly, the solution selected must lead to the recovery of valuable resources for beneficial use in the production process following the principles of circular economy.

#### *5.2.1 Biogas production*

The high BOD and appreciable concentration of nutrients (total nitrogen, phosphorus and potassium) and solids suggest the presence of considerable amount of organics which could serve as nutrients for microbial community in anaerobic digesters. Quah and Gillies [48] reported that anaerobic digestion of 1m3 of POME could generate 28m3 of biogas with 65% methane content. For small-scale palm oil mills in Ghana, the wastewater generated from the processing of one liter of crude palm oil could produce about 16–53 liters of biogas with 10.4–34.4 liters of methane content. Implementation of technologies to generate green energy would reduce the dependence on smoke-producing fuel wood which affects the health of the mill workers. Moreover, tapping the biogas for beneficial use would reduce the release of greenhouse gases into the environment.

#### *5.2.2 Solid fuel production*

Conversion of agricultural waste products into solid fuel has attracted attention and research. Empty fruit bunches, palm pressed fiber and sludge from palm oil mill wastewater are potential products for use as fuel. As has already been mentioned, limited quantities of EFB are dried and used as fuel by the small-scale mills. The suspended solids which contain solids and oils could be dried and used as solid fuel in the processing operations. The presence of unrecovered oil in palm pressed fiber is reported to enhance their combustibility and use in starting fires at the palm oil

#### *Small-Scale Palm Oil Production in Ghana: Practices, Environmental Problems and Potential… DOI: http://dx.doi.org/10.5772/intechopen.106174*

processing mills [49]. The potential of drying palm oil mill sludge and empty fruit bunch fiber for use as solid fuel has been reported by Awere, Bonoli [50]. Research must be directed at exploring different ways of converting the solid waste products into solid fuel which could be utilized in the production process or sold out to other industries.

#### *5.2.3 Co-composting*

Composting is the decomposition of organic residues into manure using a consortium of microorganisms (bacteria, actinomycetes and fungi) in a controlled environment. The high organic solids and appreciable nutrients content of POME [33, 47, 51] makes them potential substrates for compost production. In composting, wet substrates such as POME, low moisture bulking agents are required [52, 53]. POME may therefore be co-composted with bulking agents such empty palm fruit bunches and sawdust. Co-composting of POME with empty fruit bunches or saw dust has shown considerable success both at the laboratory and field scale. At a field-scale, Baharuddin, Wakisaka [54] co-composted partially treated POME from anaerobic pond with shredded empty fruit bunches (ratio of 1:3) over a 60-day period. The characteristics of the final compost showed considerable amounts of nutrients (carbon, nitrogen, phosphorus, potassium, calcium, magnesium, sulfur, and iron), trace amounts of manganese, zinc, and copper but very low levels of heavy metals. In a related study, palm oil mill sludge was co-composted with sawdust (1.86:1) over a 90-day period [55]. Through a pot experiment, the compost improved the growth of pseudostems of Cymbopogon citratus cultivated in a sandy soil.

Co-composting of POME significantly reduces the emission of greenhouse gases due to the aerobic decomposition process employed [56, 57]. The favorable climatic conditions of Ghana could enhance the compost production. The filtrate from the composting station could be assessed for their potential as liquid fertilizer.

#### *5.2.4 Vermi-composting*

An alternative to the conventional composting is vermi-composting which uses earthworms. Vermi-composting has been found to exhibit a higher rate of organic degradation and produce nutrient-rich compost with finer texture [58]. The composting period could be 50% of the time required by conventional composting systems. Composting of POME using earthworms has shown a great potential. Syirat, Ibrahim [59] used epigeic earthworms (Eudrillus eugeniae) to decompose POME sludge in a closed system within 60 days. They obtained a compost of high nutrient content compared with compost produced from EFB-POME sludge and mesocarp fiber-POME sludge. Similarly, Rupani, Embrandiri [60] used Lumbricus rubellus for vermicomposting POME-palm pressed fiber (1:1) over 30 days. The resulting compost showed significant improvement in nitrogen, phosphorus, and potassium content with 75% vermi-compost extract enhancing germination of mung bean. In another study, various compositions of empty fruit bunches and POME solid were vermi-composted using Eisenia fetida earthworms for 84 days [61]. In their study, a significant increase in total Kjeldhal nitrogen (0.4–1.7 mg/kg), total phosphorus (0.2–1.4 mg/kg) and total potassium (0.06–0.5 mg/kg) was recorded for all vermi-compost with the highest increase recorded for 1:1 EFB-POME solid combination. Vermi-composting produces two (2) important end products: manure/compost and earthworm biomass. The latter could be processed into protein source and sold to poultry and fish farmers [62].
