March 29, 2024
Global Renewable News

It's a Gas, Gas, Gas…
Volume 4 - Issue 25

November 21, 2013

Some time ago, in a Global Renewable News article, I mentioned Paul and Fritz Klaesi, a dedicated pair of Ontario, Canada dairy farmers who realized that, apart from milk, their cattle were producing gold – in the form of manure.

In 1995, the brothers built a 34 metre diameter by 3.7 metre deep concrete manure storage tank to rid them of the unwanted challenge of an existing solid storage pit and the associated runoff from the waste dropped by 142 cattle. This was one of the first steps in preparing their farm for an anaerobic digester (AD)* that would eventually produce the fuel to run a generator that would, in turn, run their farm.

In 2002, after studying plans for a digester they were familiar with in their native Switzerland, they started pouring concrete for a 500 cubic metre capacity structure. The walls are an insulated reinforced concrete and Styrofoam sandwich system coated with an acid-resistant compound. The floor of loose-fitting boards covered with loose-fitting insulation separates the digester portion from the gas storage, which is covered with a synthetic rubber, UV resistant, elastic polymer fitted into slots along the top of the walls. Agitators are positioned at each end to aid in the breakdown of matter. The digester holds the manure an average of 30 days at a temperature of 40 degrees Celsius, producing some 425 cubic metres of biogas per day.

Their 100 horsepower, 65 kW generator was originally designed to run on either diesel fuel or biogas that is generated from landfill sites so is the perfect choice to meet their needs. It produces about 300,000 BTU/h (88 kW) of heat which is collected through a single heat exchanger that links to three other units. One link collects the actual heat given off by the engine and the others collect the hot exhaust. This heat is transferred to the digester to maximize and maintain its operating efficiency.

The engine starts and warms up on 100 percent diesel fuel. During this time the generator is producing 6 kWhr of electricity and the engine is using 5 litres per hour of diesel fuel. When the generator is synchronized with the electrical power grid, an automatic controller connects to the grid and the computer controlled gas valve starts to introduce biogas so that the generator is producing 50 kWhr with 6 kWhr coming from diesel fuel burning at 5 litres per hour and 44 kWhr from biogas.1 Timers turn on the unit at peak times during chores and milking in the morning and afternoon to a total runtime of 12 hours per day. The digester generates an average of 450 kWhr of electricity per day. In the summer total consumption is about 550 kWhr and in the winter daily use is about 480 kWhr.

Paul and Fritz are able to reclaim about 48 percent of the biogas energy in the form of heat and 36 percent as electricity. The rest is lost. An outdoor furnace is fed by the heat to warm the farmhouses. However, once the ambient temperature falls below minus five degrees Celsius, wood has to be added to augment the output of the furnace. About 60 percent of the hot water and over 70 percent of the heat for their two farm houses is provided by the system.

The Klaesis have a ‘net metering’ agreement with Hydro One, Ontario's major generating company. Under the agreement they are limited to producing 50 kW of power. Net metering measures the energy used against the energy generated, resulting in a ‘net’ energy total from which their bill is calculated. Excess generation cannot be carried forward beyond the meter reading and billing period. Hydro One will not pay for excess generation. A special hydro meter shows what is produced on the farm compared to what is used. Net metering is suitable for customers wishing to reduce their energy costs by producing their own electricity and, in effect, selling it back to Hydro One.

The anaerobic digester cost approximately CA$180,000 plus labour inputs from the Klaesis. The power and control system was purchased from Switzerland for approximately CA$110,000. With the digester generating 450 to 550 kWh per day and a replacement electricity rate of 12 cents per kWh, the digester produces CA$20,000 of electricity per year, resulting in a 10 year payback on electricity savings. Through homogenization and mineralization weed seeds and many pathogens are destroyed in any ‘digested’ manure that’s used as fertilizer. This results in a win-win with substantial savings to pocketbooks – as far fewer herbicides are needed – and the environment is relieved from undue contamination.

While many digesters are being fed with the likes of rolled oats that have already been through the beast, some eleven thousand kilometres away in Ghanaur, India rice straw is the organic material of choice to feed the Punjab Biomass Power operation. The 109,000 tonnes of material devoured by the power plant each year would otherwise be burned by the local farmers contributing to the country’s already oppressive air pollution problems. Twelve megawatts (MW) of electricity is directed into the state’s power grid. Make no mistake, the plant produces emissions, although its filters reduce the amount that outdoor burning would produce. Such biomass energy is considered carbon-neutral because the fuel the plants use – like sugar cane pulp and nut shells – has already removed carbon from the atmosphere as it grew.

Because biomass power plants are eligible for carbon credits that translate into cash, Punjab Biomass will earn hundreds of thousands of dollars per year. About 60 percent of India’s population relies on agriculture for its living so ‘agro-waste’ is plentiful to the tune of 545 million tonnes. Punjab Biomass pays 15,000 farmers about CA$20 per hectare of rice straw.

The energy needs of 1.2 billion people, however, are staggering. Alternative power sources, such as wind, solar, thermal, and tidal wave, along with biomass, produced less than 12 percent of India’s power in 2012. Coal accounts for some 57 percent and to augment the rest of its requirements, the country imports about 70 percent of its oil and natural gas. Prime Minister Manmohan Singh is feeling the heat – or not – and has called for the power industry to grow its generating capability from nonconventional sources from 25,000 MW in 2012 to 55,000 MW by 2017. Biomass has the potential to generate in excess of 18,000 MW.

Agro-waste transportation challenges and bureaucratic inefficiencies notwithstanding, eight more rice-straw energy plants, each designed to produce 96 MW, are planned to be on line by 2017. A Punjab Biomass partner hopes to establish as many as 20 biomass plants generating a total 240 MW during the next three years and about 1000 MW in the next six years.

The installation on the Klaesi dairy farm and the efforts in Punjab are but two of thousands of earth-saving biomass projects underway across our World. They all bear testament to one of the key things we must continue to do to secure our energy future – Waste not! Want not!

*AD is used in agricultural, municipal, and industrial systems to treat organic materials. The process typically holds the material in an oxygen-free environment for anywhere from two to 20 days at a temperature of 30 to 60 degrees Celsius. The subsequent breakdown of the materials produces biogas, consisting of methane and carbon dioxide.

1 Don Hilborn, P. Eng., and Harold K. House, P. Eng., “A Small Scale Anaerobic Digester Operating in Ontario” Ontario Ministry of Agriculture and Food (2010): 5-6

For more information

Terry Wildman

Terry Wildman
Senior Editor
terry@electricenergyonline.com
GlobalRenewableNews.com