Forms and solubility of plant nutrient elements in tropical plant waste biochars

Abstract

Thailand is an agriculture-based country which produces large amounts of agricultural waste. Making biochar from this waste can reduce pollution, decrease costs of production, and increase C sequestration. The agronomic benefits of biochar are partly derived from the available plant nutrients in biochar. This study investigated the fertilizer value of biochars manufactured by slow pyrolysis. Pyrolysis temperature and feedstock type affect nutrient concentrations and nutrient element speciation in biochar. The physio-chemical, mineralogical and structural properties of biochars made from 14 agriculture wastes (soybean cake, corncob, lemon peel, sugar palm fibre, durian shell, tamarind wood, coconut fibre, coconut shell, bamboo wood, rice husk, eucalyptus wood, oil palm fruit, coffee waste, and bagasse) were investigated. The plant nutrients in biochar mostly occurred in crystalline minerals which were present on the surface and inside the cell structure of biochar. Most biochars examined in this research contained calcite (CaCO 3 ). The presence in biochars of several K-minerals [archerite (KH 2 PO 4 ), chlorocalcite (KCaCl 3 ), kalicinite (KHCO 3 ), pyrocoproite (K 2 MgP 2 O 7 ), struvite-K (KMgPO 4 × 6 H 2 O), and sylvite (KCl)] encourages the use of biochar as a K-fertilizer. Fibre, fruit and wood biochars contained considerable amounts of K, Ca, and P. Sugar palm and coconut fibres also contained high level of Na in halite. This study recommends the utilization of biochars manufactured from sugar palm fibre, coconut fibre, durian shell, and oil palm fruit as fertilizers. With their appreciable contents of plant nutrients in highly to moderately soluble compounds these biochars should be effective fertilizers, especially for use by organic farmers who cannot use any chemical fertilizers.

Comparative study between physicochemical characterization of biochar and metal organic frameworks (MOFs) as gas adsorbents

“…XRD analysis indicates the crystalline salts (minerals) of biochars and MOF‐5 (Figure ). Two narrow, sharp peaks in MOF‐5 around 12° and 17° were attributed to zinc hydroxide (Zn(OH) 2 ) .…”

Most Plant Nutrient Elements Are Retained by Biochar in Soil

“…Mangosteen shell, pineapple peel, and eucalyptus wood wastes were chosen for this research as they exist in large volumes in many tropical countries [2]. They were dried to 20-30% moisture before the carbonization procedure.…”

“…Biochar may contain substantial amounts of plant nutrient elements, and at normal rates of application of biochar to crops, it may act as a multi-element fertilizer [1,2]. The solubility in extractants of the nutrient compounds (minerals) within biochar and dissolution of these minerals in soils is commonly low due to the intrinsic properties of the minerals and their protected positions within the microporous fabric of biochar [3,4].…”

Optimization of Blended Biochar Pellet by the Use of Nutrient Releasing Model

“…It might be assumed that Mg, NH 4 -N, and PO 4 -P in the biochar and pig manure compost could be synthesized to struvite [Mg (NH 4 ) 2 PO 4 •6H 2 O] as slow-release fertilizer during processing time of biochar pellet. Prakongkep et al (2015) reported that the soluble compounds of total Mg and total P contained 1% to 21% and 1% to 33%, respectively, in biochar [33].…”