Hawaii

A Modified Deep Litter Waste Management System -
The Kealia Farms Model

New animal waste management systems are helping hog producers in Hawaii deal with the costly and potentially polluting aspect of hog farming. Among new systems, the Modified Dry Litter Waste Management System has a definite advantage. This model, unlike traditional water-based waste management systems, does not use water to wash down the pens and transport animal waste to a storage lagoon, which can be a major pathway for surface and groundwater pollution.

An interagency team convened by the Hawaii Association of Conservation Districts and supported by a 319 grant, developed a Hawaiian style waste management system by modifying the dry litter waste management systems currently being tested in other land- limited countries, for example, the Netherlands and Japan. In this system, the hogs are housed in sloping pens and dry litter or bedding is used to help push the waste down slope into a composting or storage pit. Various slope ratios and types of dry litter help determine the effectiveness of the system and the quality of the composted product.

How the system works

The Kealia Farm's model significantly improves the original dry litter waste management system by incorporating pen sizes with slopes ranging from 15 to 1 to 20 to 1. The optimal pen size for these slope ratios are 8 feet by 16 feet, which is typical of pen designs used in the United States (but smaller than a typical pen in Japan and the Netherlands).

Wood chips and grass cuttings were used as litter; both are excellent bedding materials for the hogs and keep the pens dry, but the Kealia and Masazu Farms (in Kona District, Hawaii) achieved their best results using macadamia nut (Macadamia integrefolia) husks. The hogs crush the bedding materials and the manure with their hooves; the mix dries and begins to decompose (compost), and it eventually moves down slope into a composting or storage pit, where high temperatures finish the job.

Temperatures in the composting pit range on average from 140 to 150 F. When the team analyzed the cooked, or composted, product, it contained 2.6 percent nitrogen, 0.6 percent phosphorus, and 2.6 percent potassium with a carbon to nitrogen ratio of 13:1 making it a good medium for organic farming. A typical pen operated under this system can convert about 30 cubic yards of green waste into 20 cubic yards of valuable compost annually.

Healthy hogs

As the green waste is an excellent bedding for the hogs and keeps the pens dry except where the hogs are watered, the modified dry litter waste management system also produced healthy hogs. In fact, feeder hogs produced under the modified dry litter waste management system easily matched and exceeded the industry's national production standard. Feeder hogs in the modified dry litter pens averaged a daily weight gain of 1.20 to 1.69 pounds; the national standard is an average daily weight gain of 1.25 pounds. During the trials, small feeder hogs entered the system weighing an average of 22.0 lbs. A typical system has 16 pens (Fig. 1). Each pen can be stocked with 30 wean-offs at the beginning of the growth cycle, then each group can be subdivided as they reach heavier wights to prevent overcrowding.

Environmental and other assets

Because it does not rely on wash downs to move the waste out of the pen and subsequently to a lagoon or storage tank, the modified dry litter waste management system eliminates one of the major potential sources of contaminated runoff on the farm. And it has other attractive benefits: lower water bills and labor costs to the farm because pen washing is virtually eliminated.

Odor production is practically nil. Hydrogen sulfide levels recorded throughout the production and storage areas were considerably less than the conventional wash down or scrapper system. The dry litter waste management facility produced 10.7 parts per billion hydrogen sulfide levels and 5.0 parts per billion in the production and storage area. The control or conventional wash-down facility had measurements of 54.3 parts per billion and an average of 104.5 parts per billion at the effluent entry to the waste lagoon. The modified dry litter waste management system succeeds in turning a potentially polluting waste product into a lucrative income stream. A yard of compost imported from the mainland United States normally sells for about $100 per cubic yard including freight costs. The organic farmer on the island of Hawaii can obtain similar material at farms with the modified dry litter waste management system at approximately one-third that price. Therefore, each pen can produce about $660 of compost annually.

Expanding benefits

The prospects are bright that as more farmers learn about the system, other hog farms in Hawaii will install modified dry litter waste management systems. The technology is scheduled to be exported to the rest of the Pacific Basin Islands supported by additional section 319 funding.

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