Energy : Effluent power goes high-tech
By Anne Lee
A Christchurch company has begun a farm-scale trial of a system that can use effluent to make electricity, heat water and cool milk.
BioGenCool, produced by Natural Systems, is projected to cut around one third off the electricity bill for farm dairies. At the same time it will provide rapid and constant milk cooling, improve the quality of the effluent, reduce greenhouse gas emissions and reduce water use.
Landcorp Farming is about to trial the system on its 850-cow Waimakariri dairy farm near Christchurch.
Landcorp research and development spokesman Collier Isaacs said it hoped to prove the system at a commercial level. As energy efficiency was becoming more important Landcorp wanted to get in behind the project.
Natural Systems director Ian Bywater said the system would be installed on the property this season and intensively monitored throughout next season.
Bywater is an electrical engineer and intensely interested in renewable energy. In order for the dairy industry to succeed in New Zealand he believes sustainability is imperative.
“The marriage of three highly innovative New Zealand technologies acting in concert has a very real benefit of lifting dairying in this country to a world's best practice level,” he said.
In 2003 Bywater won the New Spirit Challenge run by the Institution of Electrical Engineers in London with his concept of linking a biogenerator with ice bank technology.
In the BioGenCool system, effluent from farm dairies is fed to a biodigester. This is essentially a heated tank where oxygen is excluded to allow anaerobic bacteria to break down the odour-causing volatile organic compounds in the effluent. The process produces methane-rich biogas which can be used to power an engine, in this case a generator.
The electricity continuously powers a refrigeration unit which creates the ice bank. Water from the ice bank is circulated at 0°C to a plate heat exchanger where it rapidly cools the milk to 3°C. The warmed water returns to the ice bank, melting ice and allowing more water to circulate back to the heat exchanger. By the end of milking most of the ice will have melted and the process of building up ice will begin again.
Bywater estimated that by using this system, power could be reduced to one sixth of that normally used to refrigerate a milk vat.
By snap cooling the milk on the way into the vat, the issue of having warm new milk lifting the whole vat temperature is avoided. Additional energy used in refrigerating a full vat of warmed milk is eliminated.
By comparison, the milk cooled by the ice bank will remain at 3°C from the point just before it enters the vat and while it is stored there, right up until the tanker collects it.
Bywater said that as well as reduced electricity costs, potential costly thermoduric grades are also avoided. Milk foaming, a potential problem during transport, is also believed to be reduced by the rapid cooling. And spraying digested rather than raw effluent over pasture gives greater nutrient value. Having a dual fuel generator using diesel and biogas on farms can also reduce the risk of power outages.
As well as cooling, the system also heats that heat from the refrigeration process water-cooling and exhaust system of the generator. This is used to keep the biodigester at operating temperature and to heat cleaning water. Each of the component technologies has been independently developed by other companies but Bywater's patented design combines them into one.
The biodigester is produced by Waste Solutions in Dunedin, the dual diesel engine generator is supplied by DieselGas International of Wellington and the ice bank system is produced by Ice Solutions of Gisborne.
The effluent remains in the digester for 10 to 14 days, after then can be spread directly on paddocks. The pasture can be grazed almost immediately.
Bywater said studies in Europe have found that nitrogen (N) uptake by plants from the digestate material is more efficient than from the raw effluent.
Wash-down water is separated from the solid effluent waste before it goes into the digester, and is recycled.
Bywater said the system meant electricity savings for farmers as well as reducing the peak load on their electricity transformers and the rural supply network. He would not put definitive values on savings until the system has been extensively monitored on the Landcorp farm.
A price is not yet available. Initial modelling indicates the payback period for farmers could be three to five years.The system could be available in two to three years. D
© Copyright NZ Dairy Exporter February 2007
www.dairymag.co.nz
A Christchurch company has begun a farm-scale trial of a system that can use effluent to make electricity, heat water and cool milk.
BioGenCool, produced by Natural Systems, is projected to cut around one third off the electricity bill for farm dairies. At the same time it will provide rapid and constant milk cooling, improve the quality of the effluent, reduce greenhouse gas emissions and reduce water use.
Landcorp Farming is about to trial the system on its 850-cow Waimakariri dairy farm near Christchurch.
Landcorp research and development spokesman Collier Isaacs said it hoped to prove the system at a commercial level. As energy efficiency was becoming more important Landcorp wanted to get in behind the project.
Natural Systems director Ian Bywater said the system would be installed on the property this season and intensively monitored throughout next season.
Bywater is an electrical engineer and intensely interested in renewable energy. In order for the dairy industry to succeed in New Zealand he believes sustainability is imperative.
“The marriage of three highly innovative New Zealand technologies acting in concert has a very real benefit of lifting dairying in this country to a world's best practice level,” he said.
In 2003 Bywater won the New Spirit Challenge run by the Institution of Electrical Engineers in London with his concept of linking a biogenerator with ice bank technology.
In the BioGenCool system, effluent from farm dairies is fed to a biodigester. This is essentially a heated tank where oxygen is excluded to allow anaerobic bacteria to break down the odour-causing volatile organic compounds in the effluent. The process produces methane-rich biogas which can be used to power an engine, in this case a generator.
The electricity continuously powers a refrigeration unit which creates the ice bank. Water from the ice bank is circulated at 0°C to a plate heat exchanger where it rapidly cools the milk to 3°C. The warmed water returns to the ice bank, melting ice and allowing more water to circulate back to the heat exchanger. By the end of milking most of the ice will have melted and the process of building up ice will begin again.
Bywater estimated that by using this system, power could be reduced to one sixth of that normally used to refrigerate a milk vat.
By snap cooling the milk on the way into the vat, the issue of having warm new milk lifting the whole vat temperature is avoided. Additional energy used in refrigerating a full vat of warmed milk is eliminated.
By comparison, the milk cooled by the ice bank will remain at 3°C from the point just before it enters the vat and while it is stored there, right up until the tanker collects it.
Bywater said that as well as reduced electricity costs, potential costly thermoduric grades are also avoided. Milk foaming, a potential problem during transport, is also believed to be reduced by the rapid cooling. And spraying digested rather than raw effluent over pasture gives greater nutrient value. Having a dual fuel generator using diesel and biogas on farms can also reduce the risk of power outages.
As well as cooling, the system also heats that heat from the refrigeration process water-cooling and exhaust system of the generator. This is used to keep the biodigester at operating temperature and to heat cleaning water. Each of the component technologies has been independently developed by other companies but Bywater's patented design combines them into one.
The biodigester is produced by Waste Solutions in Dunedin, the dual diesel engine generator is supplied by DieselGas International of Wellington and the ice bank system is produced by Ice Solutions of Gisborne.
The effluent remains in the digester for 10 to 14 days, after then can be spread directly on paddocks. The pasture can be grazed almost immediately.
Bywater said studies in Europe have found that nitrogen (N) uptake by plants from the digestate material is more efficient than from the raw effluent.
Wash-down water is separated from the solid effluent waste before it goes into the digester, and is recycled.
Bywater said the system meant electricity savings for farmers as well as reducing the peak load on their electricity transformers and the rural supply network. He would not put definitive values on savings until the system has been extensively monitored on the Landcorp farm.
A price is not yet available. Initial modelling indicates the payback period for farmers could be three to five years.The system could be available in two to three years. D
© Copyright NZ Dairy Exporter February 2007
www.dairymag.co.nz