Overview
This report is a background knowledge source on using grapevine waste to produce biochar for vineyards to improve water use efficiency. Grape stalk biochars held more water than pruning biochars, and water retention generally increased with pyrolysis temperature (400–700°C). In laboratory tests, biochars held water similarly to sandy-loam to loam soils, so the report considers added benefit in loam vineyard soils unlikely. They outperformed typical sandy soils, but this was untested in vineyards. Unexpectedly, calcium-rich pruning biochar adsorbed over 10 times more phosphate than other unmodified biochars, suggesting potential as a slow-release fertiliser.
The most exciting finding from this study was related not to water efficiency (the main focus of the project) but rather to phosphorus adsorption. Due to the naturally high calcium content of biomass feedstocks investigated in this work, both vineyard pruning and grape stalks displayed phosphorus adsorption capacities more than 10 times that of other natural unmodified biochars in the literature, with Padthaway feedstocks having the highest calcium content of the four regions studied. Further research is recommended to explore this regional aspect, and to determine if biomass feedstocks can be further enhanced or fine-tuned (either by selection based on regional characteristics or by engineering intervention) to optimise a biochar with superior phosphorus adsorption capacity. Favorable results from optimisation studies could be used to inform the development of a subsequent large-scale project involving field application or pot trials to assess the impact of soil enrichment with grape stalk and vineyard pruning derived biochars. As with the present study, the continuous pyrolysis equipment to be used in this project is suited to mobile in-the-field use, and so would mitigate feedstock transportation costs which must be considered in all biomass applications. The economic and environmental benefits from a superior phosphorus adsorbent could be substantial and may be worth further investigation.
Abstract
The Australian wine sector generates substantial quantities of vineyard biomass waste including vineyard prunings and stalks. The objective of this project was to pyrolyse these materials to produce biochar, and then characterise the treatment effects on biochar physical properties and water-holding capacity. Biochar addition to sandy vineyard soils may improve water holding, however further testing is required. Vineyard pruning biochars displayed vastly superior phosphorus adsorption compared with other studies and may have substantial economic value as a slow release fertiliser. Further research to explore regional effects and optimisation opportunities is recommended.
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