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GILA COUNTY – Guests from the Pinetop-Lakside Sanitary District brought specialized equipment to Globe last week, spending Monday and Tuesday at Russell Gulch Landfill and sharing their recipe for converting shredded paper and cardboard into compost — once mixed with treated wastewater sludge, shredded wood pulp, and just enough water to stimulate anaerobic bacteria.
Gila County Landfill and Recycling Manager Kenny Keith arranged the project, one that’s a priority to Gila County’s District 2 Supervisor Tim Humphrey.
“The recipe for compost requires air, moisture and food,” explained Pinetop-Lakeside Sanitary District Manager Dave Smith, as a front-end loader dumped alternate bucket-loads of each ingredient into a tractor-powered blender. “Food balance includes a carbon-to-nitrogen ratio of about 30-to-1. The nitrogen source comes from our dewatered sludge and carbon source comes from wood chips and paper products. Dewatered sludge typically has a carbon to nitrogen ratio of 10 to 1, so extra carbon is required. Wood chips also provide bulk to the piles, which allow air movement to all the microorganisms. The moisture content needs to be between 40-and-60% for the process to work properly. For this pilot project and experiment in Gila County, we used about 400 pounds of shredded paper and cardboard, another 7,000 pounds each of dried sludge and green waste – and about 300 gallons of water. These numbers are for each batch, we did 10 of them — or approximately 100 tons of compost.”
Guests at last week’s demonstration saw a stainless steel thermometer probe stuck in the pile of mixed ingredients. Federal regulations for compost call for temperatures above 131-degrees for three days, a prolonged period to kill pathogens. Fortunately, producing heat is a natural part of the compost process, and bacterial action began nudging temperatures upwards that very day.
Could a composting program extend landfill life, and provide a local use for both recycled paper and ‘biosolids’ that remain after wastewater treatment? Those are among goals, according to Gila County Supervisor Tim R. Humphrey, District 2.
“Gila County Public Works has been a leader in recycling paper for the past two decades – and we’re still trying to find ways to prevent paper and cardboard from going into the landfill,” said Supervisor Humphrey. “This pilot project is an innovative way to continue making use of both paper and cardboard — and locally, as compost, mixed with shredded tree branches and limbs, plus treated sludge from the Town of Miami. This is also a partnership — bringing together the Arizona Department of Transportation and the Town of Miami. Goal is for a final product that is environmentally safe and useful compost.”
Gila County has recycled paper for nearly two decades. Despite the recent collapse of the recycling market that ended curbside pickup here in Globe, Russell Gulch Landfill continues to collect paper at a big blue roll-off reserved for that purpose near the scalehouse.
Gila County Landfill and Recycling Manager Kenny Keith had studied the Pinetop-Lakeside Sanitary District compost process, inviting the District Manager and his staff to Globe last week. “They’ve been composting since 1990,” said Keith, “finding ways to make use of biosolids produced by the District’s wastewater facility, along with paper collected for recycling. The District produces exceptional quality Class A compost that meets federal and state requirements for testing and monitoring.”
He added: “we record the temperatures of each pile. The goal is to have the temperatures above 131 degrees for three consecutive day, then we will turn the piles and the process starts over — repeated five times . Now its all mixed together and with enough water added, we’ll monitor temperature of the pile of compost, using a tractor to turn the pile every three days. We monitor and turn the piles until the required time and temperature conditions are met, then we’ll let it sit and cure for several weeks, while bacteria within the compost finish their work and the process is complete.”
Once dried, the compost is screened, any larger wood chips that remain are reclaimed for use in the next batch. Compost that passes laboratory coliform analysis is ready for use. Pinetop-Lakeside Sanitary District Manager Dave Smith adds that compost is also tested for Metals, Nitrate, Ammonium, Organic Nitrogen and hazardous waste (40 CFR 261).
“The District has been involved in composting for close to 30 years,” said Smith. “The process has evolved and the ingredients have changed, but the main points of composting, food, moisture and air are what drives the process always has to be in balance. Improvements over time are mainly to reduce costs, gain efficiencies and protect the environment. The District Board has had several discussions over other processes or methods for handling sludge, but compost continues as the priority.”
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