Organic wastes including animal manure, domestic wastewater sludge, and palm oil mill-based byproducts are predominantly used as fertilizers and require aerobic composting treatment to convert the plant nutrients into plant usable forms before using them in the agricultural fields. The aerobic composting process is time consuming, releases unpleasant odors, and the sludge product output is difficult to apply on a large scale. Moreover, the organic sludge wastes, which contain beneficial plant nutrients, are discarded. There is an immediate need for a process to prepare fertilizers from nutrient-rich waste streams.
The above mentioned need can be met through a simple process of converting the waste into solid soil conditioners or fertilizers in short durations and can be further applied in the field by broadcasting}. Additionally, the solid soil conditioners can be made into slow release fertilizers (SRFs) that can provide nutrients in low doses over longer periods of time to enhance the nutrient utilization efficiency and crop yield and also reduce the root burning process. These SRFs also reduce nutrient leaching and run off.
The technology is valuable to industries that generate sludge wastes and spend on disposing them. It will also be useful to compost producing companies that can benefit from a value added product generated from a fast process. The advantages of the process are that it is completely environment friendly, consumes low energy, and is cost effective.
The process comprises of mixing liquid wastes with solidifying agents or plasters to form a mixture of a pre-determined nutrient level. A pH modifying agent is further added to this mixture to form a pH regulated soil conditioner or a SRF. This product can be added to soil to improve its physical qualities and to provide nutrients to the plants. The production line consists of storage silos, charge-in silos, conveyor belts, mixers, pelletizers, and a packaging system. The process mixes the necessary ingredients to enable instantaneous solidification and slow release property, and achieve nutrient balance of the sludge wastes.
The product obtained is used in agricultural and landscaping industries. The slow release fertilizers have the potential to slowly release nutrients to plants including indoor flowers and vegetables. SRFs also have horticultural applications which involve supply of nutrients to lawns, outdoor gardening plants and many indoor grown houseplants. SRFs have better nutrient supply flexibility and they ensure steady and strong growth of plants for a longer time.
Slow release fertilizers are highly beneficial to plants as compared to the traditional rapid-action inorganic fertilizers, however they tend to be more expensive due to the use of polymer coatings which gradually release the nutrients over extended time periods. By enabling a different strategy, the above mentioned process is able to market SRF at a lower price than its competitors. Malaysia and Indonesia have a combined oil palm plantation area of 15 million hectares and there are at least 800 palm oil mills in this region, all of which are a huge opportunity for the generation of SRFs.
The price of SRF is lesser than that of the commercial NPK fertilizer on the basis of amount of Potassium Oxide (K2O) in fertilizer. The K2O requirement for every palm per year is 0.5 kg lesser in SRF as compared to the commercial fast action inorganic NPK fertilizer. The annual cost per palm in the case of utilizing commercial fast action inorganic fertilizer is $7 to $ 10 per palm per year and the annual cost per palm in the case of utilizing SRF is $ 8.48. The benefits of using SRF were proven in a trial conducted on the effect of using SRF on palm oil plants in Malaysia. The trial revealed better dry weight results for the plant’s fronds (+20 %), leaves (+25 %), and girth (+3.6 %) as compared to using commercial NPK fertilizer used on the same plant.