In Yorkshire, northern England, a well-known saying goes: Where there’s muck there’s brass. “Muck,” of course, is dirt, while “brass” is slang for money.
Waste-management company Toyama Kankyo Seibi K.K. (TKS) in Honshu, Japan, is using 21st Century technology to put this saying into practice every day—though it has to produce tomatoes, strawberries and flowers on the side in order to make some extra brass.
Founded in 1973, TKS collects 300,000 tons of trash from in and around Toyama city on the Japan Sea coast annually and sorts it into three types of waste: recyclable, combustible and non-combustible trash.
Currently, only metals and plastics are recycled. Plastic waste, for instance, is sorted and turned into pellets, and then processed into different types of pallets that forklifts use to shift goods about in factories and warehouses.
Combustible materials are incinerated, while non-combustible waste is transported to an adjacent landfill that will eventually be used as a site for greenhouses.
Incineration takes place in a rotary kiln—picture a long tubular tumbler-clothes-dryer, but instead of drying your washing, it burns trash at 1,000 degrees C for 90 minutes. A secondary incinerator is used to remove toxic substances such as dioxin and nitrogen oxide. By-products from incineration are buried in the landfill.
The heat from the incineration is used to generate electricity via a steam turbine. Depending on the kind of waste being incinerated, the amount of electricity produced is the equivalent of powering 600 to 700 average households a year. But rather than feeding the local grid, TKS uses the electricity to power its onsite operations.
All well and good, but nothing extraordinary to speak about so far, right? TKS’s money-making alchemy began when it decided to use the residual heat from the pressurized steam to create a side business in greenhouse horticulture. The project is part of a government scheme to help the country become a leader in hothouse horticulture using advanced technology.
Large heat-transfer containers are filled with oil that is heated using the residual heat from the steam. The containers incorporate a closed phase-change heat system filled with a heat-storing substance that changes to a solvent-like liquid when heated (the phase-change part), and which is more efficient in retaining heat than is oil.
A prepared container is transported to a nearby greenhouse on the site and is hooked up to a heat exchanger. The solvent circulates through the exchanger, and the heat is passed on and used to heat up cold water to 55 degrees C. The hot water is then pumped into the greenhouse and fans are employed to circulate air warmed by the water. Complicated, yes! But it works.
Phase-change heat transfer container hooked up to a heat exchanger with greenhouse in the... [+]
TKS currently has 28 greenhouses of different sizes in operation, the largest covering 2,500 square meters. Tomatoes represent the biggest crop, followed by flowers then strawberries.
In some greenhouses, tomatoes are grown using the Imec soilless technology method. Waterproof sheeting is laid down on the concrete floor of the greenhouse, over which is placed a drip tube that gradually dispenses and spreads liquid nutrients. A felt sheet is laid over the pipe and then comes the all-important hydrogel (water gel) membrane film developed by Imec, which absorbs the water and nutrients through nano-sized holes while blocking out germs and viruses. This is the base upon which the seeds are placed to grow.
The technique reduced consumption of water and fertilizer while accelerating sugar synthesis. According to TKS, this process leads to tomatoes with a high sugar content that are unusually sweet. However, the tomato I ate on visiting tasted ordinary.
By using advanced environmental control technology, tomatoes can be harvested at any time of the year. For instance, sensors distributed throughout a greenhouse and a mobile monitoring robot constantly record the growth process, enabling TKS to judge the best time to ship a crop. TKS is aiming to produce 500 tons of tomatoes and 1.4 million flowers annually. Tomatoes are sold to grocery stores around Japan and are also exported to Thailand.
Combined sales of tomatoes and flowers last year exceeded $6 million—not a bad chunk of brass for a side business based on trash.
