Observations of Biogas Generation and Use in Ireland and Germany - - PowerPoint PPT Presentation

Observations of Biogas Generation and Use in Ireland and Germany John Crawford

Agenda

• Introduction
• Drivers
• Energy Context
• Practice
• Engineering
• Conclusions

Introduction

• Increasing Interest for Dairy AD in NZ
• Increasing herd size
• Increasing interest in housing
• Increasing problems with effluent disposal
• Appears to be popular and successful in Europe –
• Why?
• Can we emulate that?
• What drivers?
• Scale – Also an interest for NZ municipals

Drivers

• Farm Waste Stream

Management

• EU Directive
• Profit

Drivers: Farm Waste Management

• This is almost certainly the starting point for most of the

farm based AD systems:

• Desire for improved sustainability of the farming operation
• Availability of nutrients
• Transportability of nutrients
• Odour management
• Quantity of slurry

Drivers: EU Directive & Profit

• EU Directive 2009/23/EC
• Requires member states to achieve 20% renewable

electricity generation by year 2020

• Incentives introduced to actively encourage investment
• Each State has its Own Incentives (or not)
• Profit
• Replacement of Retail energy.
• Sale of energy.
• Provision of heat energy to additional farm revenue
• enterprises. Gate fees
• Fertilizer savings

Energy Context

• Historically low levels of electricity generation by

renewable energy sources.

• Approach to incentives varies
• FIT and ROC or FIT
• Seem to be available till 20% target is reached. Then

made difficult or cut altogether.

• Typically assured payments for 20 years
• Grid operator must accept the energy – legislated – but

doesn’t have to make it easy.

Energy Context

• Northern Ireland (UK 184 units, increasing)
• ROC = £43.30
• 4 ROCs per MW.hr = £0.1732 / kW.hr, plus
• Feed in Tariff = £0.05 / kW.hr, plus heat use incentive
• Germany (8,000 units, static)
• Sliding scale of €ct6 to €ct14 / kW.hr, plus
• Various premium payments (size, feedstock, flexibility
• Maximum €ct25 / kW.hr
• Householder pays €ct20 + €ct6.5 /kW.hr as ‘Green

energy support.

Energy Context - Example

• Northern Ireland
• CAPEX £1.8M
• 500 kWel, 91% overall availability
• 400 cow herd, 6,500t @ 6%DS cattle slurry

Annual Cost Annual Revenue Feedstock, 12,000t @ £50 £600k 500x91%x24x365x£(0.173+0.05) £889k Maintenance £60k Digestate Savings on Fertilizer £20k Labour & Admin £40k Gate Fees for waste acceptance £0 Depreciation or CR @5% £90k Dried Wood Chip Revenue £ ?? Interest @4% £72k Total Annual Cost £862k Total Annual Revenue £909k ++

Practice

• Robust, well engineered systems.
• Trend is 250kW.el minimum economic and increments
• f 250kW.el. Some go lower, BUT….
• Cattle / Pig slurry used as the biological inoculum and

a low grade energy source.

• Alternative feedstocks (On & Off farm) provide the

bulk of the energy yield:

• Grass & Maize silage
• Winter wheat
• Beets
• Chicken litter
• Food & meat wastes (must be pasteurized)

Engineering

• Concrete or SS reactors
• Three styles of Gas storage:
• Double skin, pressurized bladder over headspace
• Double skin, pressurized external balloon
• Pressurized headspace under concrete roof
• Common engines:
• MVM Gas – Owned by Caterpillar
• Jenbacher
• Deutz
• Scania
• Leihberr

Engineering

• Mixing styles the key difference:
• Submersible WW mixers (Williams)
• External Recirculation & jets
• Gas Mixing (Greenfinch)
• Inclined shaft / Big blade (Weltec)
• Mississippi Paddle Wheel (Hochreiter)
• Common themes:
• CHP
• Stainless steel pipework
• Centralised pumping and maceration
• Instruments: Temp, Pressure, Gas analysis, Titration
• analyser. (Adequate, not excessive)
• Digester treated like another herd of cows

On the Farm

• An extra FTE staff member to manage the digester:
• Loading the feeder
• Monitoring operation
• Managing digestate
• Legislative and Revenue administration,
• Depending on feedstock, AD process measured as

increasing N bioavailability by 18 – 24% over that of the feedstock.

• Odour level from digestate is about 1/10th that of raw

animal slurry.

• AD reduces the mass for disposal ~21%

Conclusions

• Digester treated like another herd of cows.
• Economics of an electricity only enterprise questionable

without the incentives.

• Economics of a slurry only enterprise questionable.
• Multiple Feedstock – Multiple Product – Better Outcome
• Other revenue streams and farm operational drivers are the

key to financial viability.

• Small scale systems displacing retail energy purchase,

using the heat and improving the feedstock fertilizer value may be feasible. Assessment each on its own merits.

• In Feasibility study – look for a ‘Sweet Spot’ where the

drivers overlap.

Conclusions

• For current New Zealand context:
• We don’t yet have year round housing of cows (pigs yes).
• Collect approx. 10% of slurry.
• No incentives and low wholesale feed in tariffs.
• Is wholesale electricity more valuable than milk produced

from silage?

• The digestate would be valuable.
• Parallel, heat using enterprise may be the key as may

upgrading biogas to methane and use as a biofuel.

• Recommended Reading:
• A Review of Anaerobic Digestion Plants on UK Farms, by

Angela Bywater, for Royal Agricultural Society of England.

Acknowledgements

• Noel Gavigan, Bioenergy Association of Ireland (RoI)
• Dr Peter Frost, Agri-Food and Biosciences Institute, Hillsborough

Research Farm (NI)

• Nigel Moore, CAFRE, Greenmount Agricultural College
• Williams Industrial Services (NI)
• Edina (RoI)
• Weltec Biopower (Germany)
• Blackiston-Houston Estates (NI)
• Progressive Energy (NI)
• McDonnell Farms / GreenGas (RoI)
• Weichering Sudmann (Germany)
• Suren Meyer (Germany)
• Naturstrom Buschheide (Germany)