from batch to batch can vary widely due to the organic nature of the sources, and the different crop fertilizer needs. There are a number of promising sources for organic fertilizer. Vermicompost leachate, or worm compost tea, makes a highly nutritious fertilizer if the food and animal waste used in its production are of high quality. Since it is already liquid, it can be easily added to hydroponic systems. Similarly, a study in Japan had positive results using treated food waste as fertilizer. This study used fish-based soluble fertilizer and corn steep liquor, which are byproducts of existing food production, with success. A study from Thailand used a combination of waste molasses, distillery slop, and sugarcane leaves. After testing different ratios of these mediums, the authors found a ratio that led to growth rates comparable to those of chemical fertilizer. These methods have the added ecological benefits of being less energy intensive than inorganic fertilizer production, while diverting food waste from landfills, where nutrients are not cycled and greenhouse gases are generated as waste breaks down. Organic certification Organic certification of hydroponics has been a heavily contested topic in the agriculture industry. In the United States, which is the only country that allows hydroponic production to be certified "organic," there are no formal guidelines on organic hydroponics. In 2010, the National Organic Standards Board voted decisively against organic certification of hydroponic production. In 2018, an NOSB vote to change the NOSB's 2010 recommendation failed. The USDA refused to implement the 2010 NOSB recommendation, so certification was left to the discretion of third party certifying agents. </ref> In March 2020, Center for Food Safety (CFC) along with a coalition of organic farms and stakeholder groups filed a lawsuit against the USDA on their decision, on the grounds that hydroponic systems fail to promote soil health and therefore violate the 1990 Organic Foods Production Act. Hydroponics and aeroponics are not allowed to be labeled and sold as organic in Canada, as they do not meet the minimum soil requirements. Similarly, beginning 2021 under the revised European Union organic law, hydroponically grown crops cannot be certified organic in the EU as they are not produced in soil-based systems. Sustainability See also Organic hydroponic solutions Controlled-environment agriculture Digeponics References