Monitoring physicochemical and biological characteristics of date palm waste compost

Ouali, Abdelouahad (2025) Monitoring physicochemical and biological characteristics of date palm waste compost. Doctoral thesis, Mohamed Khider University of Biskra.

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Abstract

The date palm (Phoenix dactylifera L.) is an important crop in the MENA region, particularly in Algeria, where it is widely cultivated in areas like Biskra. This horticulture produces significant waste that needs to be recycled for sustainable development. Composting is a key method to recycle this agricultural waste, reducing reliance on chemical fertilizers and enhancing soil health. However, composting lignocellulosic wastes, like date palm waste (DPW), presents challenges due to its chemical properties that limit biodegradability. The current research utilized a cost-effective rotary drum bioreactor, which offers various advantages, to establish a decentralized system that enables farmers to manage waste effectively on their farms. Two compost preparation techniques were used. The first employed a ratio of 2:2:6 (DPW : Additives : Water) to achieve a moisture content of 60% , for 60 days composting, with poultry (PM1) and sheep manure (ShP2) as additives. The second approach accelerated decomposition by optimizing the initial moisture content and C:N ratio. A calculation technique was used to formulate a mixture with initial C:N ratios of 25 (CkS25) and 30 (CkS30), regarded as optimal for lignocellulosic composting by numerous studies, and included chicken litter as an additive for a 20-day period. To assist farmers with the mixture proportion calculations, an app was developed, taking into account their limited mathematics knowledge. In all trials, the bio-oxidation periods lasted 18 days, while the thermophilic phases lasted a minimum of 9 days. Throughout the trials, organic matter, moisture content, particle size, and wet bulk density showed a decreasing trend compared to their initial values, whereas other parameters exhibited an increasing trend. By day 20, all trial end products had a dark hue, a soil-like odor, and a low temperature. However, the germination index remained below the acceptable threshold for agricultural application (80%), with only the mixtures CkS25 and CkS30 recording a C:N ratios under 25. After 60 days, mixtures PM1 and ShP2 achieved a germination index around 80. In summary, the bioreactor and the mathematical approach proved effective in improving the initial mix; however, a 20-day period was insufficient for producing a fully mature and stable product.

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