CASE STUDY Lodge Farm

Award-winning AD for farms – that works!

In June 2000 Wrexham farmer, Richard Tomlinson, took the bold step of taking Lodge Farm and its 650 milking

cows and 1,100 acres to fully organic status. In the process he was heavily involved in forming Calon Wen, the

Welsh Organic milk co-operative that now comprises 25 Welsh farms, who have pooled resources to supply in

excess of 20 million litres of organic milk each year to market. Buoyed by the environmental and social benefits

of his organic status, Richard determined to generate all of the farm’s heating and electricity requirements on

site, thereby removing any reliance on the National Grid.

Richard’s obvious solution was to be found in Anaerobic Digestion, of which there were already a few example

systems in operation on UK farms and which were common on many continental European farms. The

additional benefits of using the copious quantities of animal slurry generated on the farm with which to

produce high quality solid and liquid fertilisers provided further motivation.

However, Richard soon recognised that these AD systems were designed to process purpose grown crops and

clean waste streams, essentially geared to producing energy only, and were not designed to cope with the two

main causes for a farm AD plant to break down and fail, namely the high levels of grit normally found in farm

animal waste and the propensity for foaming in the digester.

fre-energy

Under the umbrella of Farm Renewable Environmental Energy (fre-energy), a newly formed company

established by Richard in 2007, and with the contribution of a small Welsh Government SMART award grant,

Richard and his team have developed an AD system that resolves all of the main problems typically associated

with farm AD, namely dealing with grit laden slurries and waste crops.

Incorporating the company’s patented technology, the fre-energy system is the first in the world to be able to

continuously process wastes that contain grit, for which chicken litter is especially notable, and indeed other

contaminants such as ash, sand, soil, glass, metal and any other inorganic materials. Unlike conventional AD

plants there is no requirement for the plant to be shut-down whilst the tank is emptied of this non- bio-

degradable silt which would otherwise quickly build up over time.

fre-energy’s award winning

patented auto de-gritting and gas

activated mixing technology ensures

the digester can be run continuously

at maximum capacity. By combining

gas mixing with de-gritting there is

no requirement for the agitation to

keep silt and grit in suspension,

thereby reducing the equipment’s

parasitic use of energy and

increasing the efficiency of its gas

yield.

The fre-energy system has also been designed to deal with the otherwise inevitable problem of foaming which

typically occurs when the feed-stock is significantly changed over a short period of time or, for example,

through the addition of high-strength food wastes. When the bacteria are not given time to adjust to such

changes, they create a foam which, if it enters the gas output pipes, can irreversibly damage the VCHP engine

and compromise the AD process.

Installed within a sound- and

fire- proof container unit fre-

energy has developed its own 80

kW CHP generator based on a

standard, off-the-shelf, and

incredibly reliable six cylinder

Perkins diesel engine. Multiple

engines provide the advantage

of being able to handle

increased flexibility in gas

generation capacity, whilst

service or repair down-time is

reduced. An entire “plug and

play” unit can be replaced

within just a couple of hours.

Full control of the AD system is provided through a user-friendly Interface Control Panel colour touch screen delivering real-time status information and enabling the operating parameters to be changed at any time. With all information also being remotely monitored on-line by fre-energy, the system’s optimum performance can be continually checked and any potential issues dealt with quickly and efficiently.

When asked if it is difficult to operate an AD plant, Richard replies: “If you can feed a cow and know about

animal nutrition, then you can feed and operate a digester!”

In 2012 fre-energy’s AD solution was recognised by the UK Anaerobic Digestion and Biogas Association (ADBA) by winning the Award for “Best Integration of AD into a farming business” and, in 2013, achieved further industry recognition by being selected as a finalist in the “Organics Recycling Awards” run by letsrecycle.com.

Lodge Farm

Lodge Farm has played an important role in the local community for many years and Richard’s family has

farmed in the Holt area for five generations. In recognising the concerns that local residents might have with

the planned build of an AD plant on nearby land, the farm engaged with the local community at an early stage

to allay any fears and subsequently ensured that it kept them informed of latest developments. Local

awareness has also been maintained through news articles in the local and regional media and Open Days to

view the AD plant.

The farm has provided the location on which the equipment has been, and continues to be, researched and

developed in order that its optimum performance levels and its long term reliability have been established

whilst also now serving as a reference site.

Since the AD plant became operational in 2007, the farm processes around 9,125 tonnes of animal slurry each

year and a further 1670 tonnes of chicken litter. The feed-stocks vary according to the season, due to the

livestock being housed during winter and outside during warmer periods, and are loaded once a day into a mixing pit, to produce a homogeneous mix that can be automatically pumped over 24 hours into the 1,050 m

3

tank. In Winter the tank is fed at approximately 35 m3 per day whilst in Summer months this drops to around

18 m3, with the waste requiring just 30 days’ processing time in the colder conditions of Winter and around 58

days’ in Summer.

The mixing pit can be scaled

to meet the specific

requirements of each

individual site. It also serves

as a central drain for the

site and as a trap to prevent

any large objects, such as

stones, from damaging the

loading / chopper pumps.

The bacterial ecology in the slurry acts as an inoculant which provides stability to the AD process, allowing co-

digestion with high strength feed-stocks. The farm has now been granted a permit to allow locally produced

food waste, sourced from nearby hotels, catering establishments, shops, domestic waste and food

manufacturing plants, to be brought onto site for processing along with the slurry. This relatively small

proportion of food waste will significantly increase the biogas yield levels of the plant, thereby improving still

further its Return On Investment.

Using fre-energy’s own high through-put

separator, which has been designed to

avoid the difficulties that standard

agricultural separators have when

processing the typical volume and

composition of digestate, the digestate is

separated into its solid and liquid

fractions.

Following efficacious storage to suit the farm’s nutrient requirement, the liquid digestate, which

predominantly contains the nitrates, is applied to pasture using an umbilical cord system with a low level

trailing shoe, whilst the solid digestate, in which potash and phosphate is concentrated, is spread to land away

from home which is used for growing crops to feed the dairy herd during the winter. Through the use of an

umbilical cord the liquid fraction is applied to land away from the home that is around the farm without

incurring the energy costs normally associated with this procedure. The farm does not import any fertiliser to

grow grass or crops and is wholly served by the AD output.

Results

Item Data / Value

Digester volume 1,050m3 Average digester load 35m3 per day Winter; 18m3 per day

Summer Average residence time in digester 30 days Winter; 58 days Summer

Feed-stocks Dairy cattle slurry – 8,400 tpa Chicken litter – 1,700 tpa

Biogas production capacity Max 100 Nm3/h, feed-stock dependent Actual biogas production 75 Nm3/h

Actual electricity production 1,140 MWh pa Actual heat production 1,226 MWh pa

Digester operating temperature 40°C Digester power consumption 3kw/m3 per day

70 kw th Winter; 36 kw th Summer Biogas storage Twin membrane dome

Biogas composition CH4 65%; CO2 35%, H2S approx. 110 ppm

In processing animal slurry alone, the AD unit produces around 160 kw of electricity and 200 kw of heat of

which circa 30 kw electricity and 60 kw heat is used on site whilst the remainder is exported to the National

Grid.

Richard sums up: “Utilising the energy in farm waste, such as animal slurries and soiled crops, we can make a

crucial difference to the future profitability of food production especially in these times of rising energy and

fertiliser prices. Tonne for tonne, these wastes typically produce between four and ten times as much energy.

The fre-energy system provides a template for a closed loop nutrient cycle for sustainable food and energy

production using equipment that has been designed and built specifically for its use in farming operations.

Adopted on a broad scale, it has the potential to significantly reduce the environmental impact of the

agricultural industry whilst contributing greatly to the long term financial security of the farming community.”

in association with

Benefits

Financial Benefits

Constant generation of energy means a reduced farm energy bill.

Constant generation of fertiliser (worth a saving of approx. £340 per

tonne).

Additional income stream generated from the export of energy eg FITs

and ROCs, government financial incentives for renewable heat generation

eg RHIs, and feed-stock gate fees.

20% return on equity.

20 year equipment warranty.

Environmental Benefits

Sustainable management of on-farm slurry and waste crops, whereby

both the nutrients and the energy from these wastes are being fully

utilised.

Reduced carbon footprint.

Reduction in farm methane emissions (green-house gas properties of

methane are over 20 times more powerful than Carbon Dioxide).

Reduced reliance on, and possible replacement of, unsustainable

chemical fertilisers, herbicides and pesticides.

Improved land fertility and productivity.

Digestate has the same crop yield as synthetic fertiliser at an application

rate of 150 kg h-1, does not hinder clover growth as synthetic fertiliser

does and avoids weed seeds (Source: University of Bangor).

Nutrient availability is increased by between 20% and 25% enabling

improved nutrient uptake in comparison to undigested slurry. Separated

digestate is absorbed quickly, leaving little residue on crops and thereby

reducing rejection by livestock, evaporation, oxidation and run-off losses.

Reduction of both Biological Oxygen Demand (BOD) and nitrate leaching

into water courses.

Excess electricity generated by the plant may ultimately be used to power

local houses once the required equipment is in place.

Social Benefits

Supports the local economy.

All equipment is manufactured in the UK, the majority at Lodge Farm in

Richard’s brother’s engineering business (JFT Engineering) using 100%

renewable electricity generated by Lodge Farm Biogas.

Energy security.

Removal of potential pathogens eg salmonella and E.coli.

Odour from slurries applied to land is significantly reduced by up to 90%.

Visual impact is significantly less than that of wind turbines and solar

panels.

Noise pollution from the CHP unit is mitigated by insulation.

The principle of extracting resource value from waste streams is vital to

the future health of the planet. Copyright fre-energy © 2013