Assessing the growth-stimulating effect of tea waste compost in urban agriculture while identifying the benefits of household waste carbon dioxide

Tea is a globally popular beverage, leading to a significant accumulation of municipal waste. This study investigated the effects of tea waste compost on the growth traits of Raphanus sativus L. or radish while exploring the contribution of clean source carbon dioxide to sustainable production. The research team gathered the tea waste from urban households and allowed it to decompose for four months. Certain volumes of the tea waste compost ranging from 0% to 75% were mixed with locally available loamy textured garden soil (v/v). To simulate the impact of carbon dioxide waste from urban households on plant growth, the first greenhouse was enriched with carbon dioxide to reach elevated concentrations of 1500 +/- 100 ppm, while the second greenhouse was maintained at the ambient level of 500 +/- 20 ppm. The optimal growth temperature of both greenhouses was supplied with electricity. Using a split plot design, the effects of normal and elevated carbon dioxide levels, different volumes of tea waste compost, and the combined effect of tea waste compost and carbon dioxide levels on growth traits were investigated. The results showed that the elevated carbon dioxide level negatively influences the radish yield, biomass accumulation, and vegetative growth parameters. However, the tea waste compost improves growth traits with increasing volumes in garden soil from 0% to 75% (v/v). In the media containing 75% of tea waste compost, the elevated carbon dioxide level has the same effect as the normal level on growth traits, however, positive effects on total fresh weight but negative effects on measures of total dry weight, leaf dry weight, and total leaf area. These results show that the highest volume of tea waste compost ideally supports the growth of radish, which is mainly related to its high nitrogen content. The high and normal carbon dioxide levels in this volume are unable to dominate each other in terms of growth promotion. However, to reduce the amount of carbon dioxide emitted from houses and to produce fresh products, the waste carbon dioxide of urban houses should be transferred to the greenhouse to provide radishes with higher carbon dioxide levels during photosynthesis. Renewable energy sources such as solar or wind-generated electricity can be used to increase the temperature to the optimal level. This production method should be evaluated in future studies for other horticultural crops that prefer high carbon dioxide levels.