Purpose: To provide participants with an understanding of the sinks of carbon and sources of methane and nitrous oxide emissions in land based systems. Source: University of Melbourne (UoM) June 2013 THE MANAGEMENT OF AGRICULTURAL SOURCES AND SINKS

The management of soil based sinks Carbon sequestration in soils under a range of agricultural practices Drivers of soil carbon change Management effects on soil carbon Soil carbon monitoring

Desert soils: < 1%Agric soils: 1-5%Forest soils: 1-10% Organic soils: up to 100% In top 15 cm SOM typically ranges: Carbon forms in soil –Inorganic forms carbonates, graphite, CO 2 (carbon dioxide), HCO 3 (hydrogen carbonate ion) –Organic living, dead; labile, non-labile What is Soil Carbon?

Soil Organic Matter (SOM) –The sum total of all organic carbon- containing substances in soils: –Living biomass, decomposed residues and humus Soil Organic Carbon (SOC) –Carbon component of the SOM Total Organic Carbon (TOC) –SOC What is Soil Carbon?

Crop residues –Shoot and root residues greater than 2 mm found in the soil and on the soil surface –Energy to soil microbes Particulate Organic Carbon (POC) –Individual pieces of plant debris that are smaller than 2 mm but larger than mm –Slower decomposition than residues –Provides energy and nutrients for microbes What is Soil Carbon? Source: Jeff Baldock

Humus –Decomposed materials less than mm that are dominated by molecules stuck to soil minerals –All soil processes, source of N Recalcitrant or resistant organic carbon (ROC) –Biologically stable; typically in the form of charcoal. What is Soil Carbon? Source: Jeff Baldock

Why is it important? - Biochemical energy - Reservoir of nutrients - Increased resilience - Biodiversity Biological roles - Structural stability - Water retention - Thermal properties - Erosion Physical roles Chemical roles - Cation exchange - pH buffering - Complexes cations Roles of organic carbon (and associated elements) in defining soil productivity 1567 to 2700 Pg of C stored in soils worldwide Source: Jeff Baldock

Tropical forests Temperate forests Boreal forests Tropical savannas Temperate grass & shrublands Deserts & Semi-deserts Tundra Croplands PlantsSoils Area Global Carbon Stock (Pg C) Mill km Total Saugier et al (2001) How does soil carbon compare to other sinks globally?

A big, slow-changing input : output equation –Inputs: Plant residues & fire residues –Outputs: Decomposition & mineralisation Limited by –Climate, soil type, management & nutrients –Water is usually most limiting Good seasons = more soil C Drought = less soil C What determines soil organic carbon content? Source: Jeff Baldock

How fractions differ between soils Soil 1 Soil 2 Soil 3 Soil 4 Soil 5 Soil 6 Soil 7 Soil organic carbon stock (Mg C/ha) Particulate organic carbon Humus organic carbon Resistant organic carbon 0 Understanding composition provides information on the vulnerability of soil organic carbon to change Source: Jeff Baldock

Can we quantify changes? Longest experimental evidence Soil-C increase often greatest soon after land-use or management change Rate of change decreases after new equilibrium is reached. BUT 1.2% to 2.7% in 110 years = 0.013% /yr Maximum of 0.4% in 25 years Arable land  grass

The management of carbon in vegetation Carbon sequestration in trees Drivers of tree carbon change Management of tree carbon Monitoring of carbon stored in trees and woody vegetation

Carbon sequestration in trees Carbon stock/pools Carbon sequestration Carbon balance How much C at one point in time Change of C stock over time Exchange of C fluxes over time

Carbon sequestration in trees Measurement of forest carbon pools Aboveground biomass Belowground biomass Soil carbon Litter & coarse woody debris Easy, tree allometrics, remote sensing techniques good inventories Often ignored Not many data Often small pool Difficult Not many data Mostly expansion factors (i.e. 25% of aboveground) Relatively easy to measure Not many data in forests Very difficult to assess change of soil C over time

Carbon stocks in ecosystems 1) Malhi et al (1999) PCE 22: 715 & 2) Chen et al. (2003) Oecol 137:405

Drivers of tree carbon change Chapin, Matson, Mooney (2002) Carbon stocks are only one small part of the carbon ecosystem processes What will matter long-term is ecosystem production: inputs - outputs

CO 2 Gross Primary Productivity GPP (photosynthesis) Litter (foliage, branches, etc) Net Primary Productivity NPP = GPP - Ra Soil microbial respiration (Rh) Soil carbon CH 4 N2ON2O Non-CO 2 greenhouse gas (trace gas exchange) Canopy, wood & root CO 2 respiration (Ra) Net Ecosystem Productivity NEP = GPP - Ra - Rh

Drivers of tree carbon change 1) Malhi et al (1999) PCE 22: 715 & 2) Chen et al. (2003) Oecol 137:405

Drivers of tree carbon change Main drivers that influence tree carbon change: Drivers that influence tree carbon uptake (photosynthesis): Light Water availability Temperature Atmospheric CO 2 Nutrients Drivers that influence tree carbon loss (respiration): Water availability Temperature Nutrients Drivers that influence ecosystem carbon loss (disturbance): Fire Pests & diseases Storms Floods

Drivers of tree carbon change Photosynthesis > Respiration Net carbon gain Healthy mature forest Healthy young forest/plantation Photosynthesis > Respiration Net carbon gain Forest is a carbon sink

Drivers of tree carbon change Photosynthesis = Respiration Small carbon gain Old growth forest Disturbance / Deforestation Net carbon loss Photosynthesis < Respiration Forest is carbon neutral or small sink Forest is a carbon source

Management of tree carbon Important: Distinction between C-stocks and C-fluxes C-stocks  need to be conserved C-fluxes  should results in sinks not sources IPCC 2007 WG III

Management of tree carbon Mitigation options for the forest sector

Management of tree carbon Four general categories 1. Maintain or increase forest area 2. Maintain or increase stand level carbon density (t C/ha) 3. Maintain or increase landscape level carbon density 4. Increase off-site carbon stocks IPCC 2007 WG III Largest short-term gains – avoid emissions  avoid forest degradation, fire protection  once emission is avoided C stocks increase only slightly Long term gains – afforestation  up-front cost Largest sustained mitigation benefit:  maintain or increase C-stocks  produce annual yield of timber, fibre, energy

Management of tree carbon 1. Maintain or increase forest area  reduce deforestation and forest degradation IPCC 2007 WG III Protection from harvest  reduces wood and land supply  income for local communities  socially acceptable? REDD Policy Largest and most immediate impact!!!  large C stocks are not emitted if forest is maintained Mitigation cost depends on:  cause of deforestation (wood extraction, agriculture, settlement)  associated returns from non-forest land-use  returns from potential alternative forest uses (tourism)  compensation payments

Management of tree carbon 2. Maintain or increase stand level carbon density (t C/ha)  Silviculture (fertilisation, uneven-aged stand management, site prep)  tree improvement (breeding, molecular) IPCC 2007 WG III Harvest systems that maintain partial forest cover  minimize losses of dead organic matter  minimize losses of soil C by reducing soil erosion  avoid slash burning and high emission activities Economic constraints  leaving carbon on site delays revenue Forest fertilisation  potential N 2 O losses

Management of tree carbon 3. Maintain or increase landscape level carbon density  forest conservation  longer rotations,  fire management, protection against insects Landscape level changes usually sum of stand level changes

Management of tree carbon 4. Increase off-site carbon stocks  wood products  substitute products with high fossil fuel requirements  increase biomass energy to replace fossil fuel IPCC 2007 WG III Duration in wood products variable  days (biofuels)  years/decades (landfill)  centuries (furniture, houses) Replacement of fossil fuel intensive construction materials  aluminium, steel, concrete, plastics Wood-fuels can provide sustained carbon benefits  replacement of fossil fuels

Monitoring of carbon stored in vegetation Assess and monitor the extent, state and development of forests and woodlands All forest areas in Australia – Minimum 2m height and 20% canopy cover Two main components: – Ground based inventory (Tier 1) – Remote sensing (Tier 2 & 3)

Monitoring of carbon stored in vegetation Measurement of forest carbon Tree (diameter and height) Other vegetation (understorey) Coarse woody debris Stumps and dead vegetation Soil and litter Remote sensing: High resolution images (2 x 2 km) Medium resolution images (wall-to-wall)

Monitoring of carbon stored in vegetation Annual change in carbon stocks in biomass (stock-difference method) where

Monitoring of carbon stored in vegetation C = total carbon in biomass (tonnes, at time t 1 ) A i,j = Area of land in forest type i and climate zone j (ha) V i,j = Merchantable volume (m 3 ha -1 ) BCEFs i,j = biomass conversion and expansion factor (merchantable volume to aboveground biomass in tonnes) R i,j = ratio of belowground to aboveground biomass Cf i,j = carbon fraction of dry biomass (default 0.5) IPCC 2006

Monitoring of carbon stored in vegetation V i,j = Volume of tree biomass in forest type i and climate zone j Define plot area Measure over-bark diameter at breast height (1.3 m) and tree height  calculates tree stem volume Convert plot level volume to biomass using biomass conversion and expansion factors (BCEF’s) Or convert tree level dimensions to biomass using allometric equations then aggregate to plot level

Monitoring of carbon stored in vegetation How many plots do I need to measure? Voluntary Carbon Standard (VCS) and REDD+ require carbon pool estimates with 95% confidence that results are within 10% of the true mean Coefficient of variation (SD / mean, %) in a pilot survey t is student’s t value for a specified degree of certainty E is the specified precision (e.g. 10% of true mean) Total tree biomass carbon of 35 plots: mean = 92 t C/ha, SD = 27.3 CV = 27.3 / 92 = 30% t (student’s t value, 95%, CI, 35-1 df) = 1691 E = within 10% of true mean Required plot number for tree carbon: n = 25

Monitoring of carbon stored in vegetation Design of a biomass carbon estimation program will depend on objectives Within 10% of true carbon stock within a forest stratum: pilot survey and sample intensity formula  temporary plots Wall to wall prediction of carbon stocks: temporary plots combined with spatial data (e.g. remote sensing) Carbon stock change: repeat measurement of permanent sample plots (+ spatial data)

Methane from ruminants and monogastrics Introduction and background to methane emissions Global warming potential Methanogenesis in the rumen Factors affecting methanogenesis

Methane from animal production Global Trends in Atmospheric Methane IPCC 2007

Methane from animal production Australian Trends in Atmospheric Methane CSIRO 2011

Methane from animal production Unexpected rise in global methane concentrations from 2007 Mascarelli (2009)

Methane from animal production DCCEE 2011 Australian Methane Emissions

Methane from animal production Global warming potential –Shorter lifetime in atmosphere 8 to 12 years –Concentrations Pre-industrial ppb Current ppb –High GWP 72 x CO 2 on a 20 year time horizon 21 x CO 2 on a 100 year time horizon (AR2 – DCCEE) 25 x CO 2 on a 100 year time horizon (AR4) IPCC 2007

Methane from animal production Ruminants (cows, sheep) –95% breathed and eructated –5% from flatus Non-Ruminants (pigs, poultry, horses) –Mainly from flatus –Horses, rabbits Extended caecum for microbial digestion Effluent ponds –Anaerobic ponds = more methane Eckard 2011

Methane from animal production Microbes in the microbial digestion –Bacteria, protozoa, fungi, archaea, and viruses 40-60% bacteria, protozoa 5-10% fungi 3% Archaea (methanogens) –Normal component of the rumen –Many species yet to be identified! Eckard 2011

Methane from animal production Methanogensis –A form of anaerobic respiration 4H 2 +CO 2 →CH 4 +2H 2 O –Uses H 2 to reduce CO 2 to form CH 4 –Volatile Fatty Acid (VFA) production produces H 2 BUT H 2 can also affect VFA production –Interspecies hydrogen transfer From bacteria and protozoa to methanogens Klieve & Ouwerkerk 2007; Attwood & McSweeney 2009; McAllister & Newbold 2009

Methane from animal production Volatile Fatty Acid production –More propionate, less H 2, thus less CH 4 –More butyrate and acetate, more H 2, thus more CH 4 Jansen 2010

Methane from animal production Waste management systems –Piggery > Dairy > Poultry DCCEE 2011

Methane from animal production Waste management systems –% of total on farm CH 4 from waste management 7% of Dairy farm 95% of Piggery DCCEE 2011

Methane from animal production Less CH 4 –Faster rumen passage –More O 2 –Less methanogens –Less H 2 –Carbon –Lower temperature More CH 4 –Slower rumen rate –Less O 2 –More methanogens –More H 2 –Acid rumen pH –Higher temperature Factors affecting methanogenesis Eckard 2011

Animal ClassMethane (kg/year) MJ CH 4 lost /hd/day Effective annual grazing days lost Potential km driven in 6-cylinder car Mature ewe6 to to to to 90 Beef steer50 to to to to 800 Dairy cow90 to to to to 1350 Methane from animal production Largest inefficiency in animal production –Methane energy content MJ/kg –6 to 10% of GEI lost as CH 4 But: we cannot abate 100% Eckard, Grainger & de Klein 2010

Methane Measurement Measurement – in vitro –Test tubes –Continuous Culture AgResearch, New Zealand

Methane Measurement Measurement –SF 6 (sulphur hexafluoride)Tracer Individual animals in the field Permeation tubes Grainger, Eckard et al Evacuated yolk/canister

Methane Measurement Measurement –Chambers/Calorimeters Individual Animals Grainger, Eckard et al. 2007

Methane Measurement Measurement –Open Path laser or FTIR tracer Wind Reflector FTIR Griffiths et al. 2007; Phillips et al Laser FTIR

Methane from landfill and waste treatment Introduction to methane production in landfill and waste Factors affecting methanogenesis Measurement of methane

Methane from landfill and waste Methane in landfill or waste –Decomposition of organic matter –Anaerobic conditions (moisture) Typically contains –50% to 75% methane –25% to 50% carbon dioxide –impurities such as hydrogen sulphide & ammonia

Methane from landfill and waste Basic approach –Covering effluent lagoons to prevent the release of methane into the atmosphere –Collecting the biogas from the covered lagoons Methane can then be –Flared to convert CH4 to CO2 (lower GWP) –Used to generate heat –Drive a steam turbine or modified combustion engine to replace fossil fuel energy

Methane from landfill and waste Some types of digesters for livestock effluent ponds –Covered anaerobic lagoon Work at ambient temperatures Less efficient in winter Suits total solids up to 3% –Anaerobic Filter Film increases surface area for digestion Suits total solids up to 3% –Continuously Stirred Tank Reactor increases contact between bacteria and organic matter Suits total solids up to 3 to 11% –Plug flow Anaerobic Digester A long concrete tank loaded at one end and plugged at the other Suits total solids up to 11 to 13%

Methane from landfill and waste Digester options for livestock effluent as determined by solids content (source: US EPA nd).

Factors affecting methanogenesis in waste and landfill Organic matter content Anaerobicity –Oxygen content –Moisture content Temperature –Optimum 20 to 50ºC

Estimating methane from waste or landfill Calculated –Piggery waste - PigBal model –Dairy waste – DGAS Calculator –Landfill gas – Baseline = methane from pond prior to any covering Project = methane after covering

Problems with methane collection from waste and landfill Water vapour Hydrogen sulphide is corrosive Methane is not easily compressed –On site consumption needed Explosive at 5 to 15% of air CO 2 and H 2 S can collect in confined spaces

Methane from waste and landfill In Summary: –Collecting methane from waste and landfill can be a valuable alternative source of energy, but does require specialist expertise and equipment for safe operation.

Nitrous oxide from cropping and animal production Introduction and background to nitrous oxide emissions Global warming potential Sources from soils, fertilisers, legumes and animal waste Factors affecting nitrous oxide formation in soils Measurement of nitrous oxide

Nitrous oxide from cropping and animal production Atmospheric Concentrations –Pre-industrial ppb –Current ppb 0.25% per year IPCC 2007

Nitrous oxide from cropping and animal production Australian Atmospheric nitrous oxide CSIRO 2011

Nitrous oxide from cropping and animal production Nitrous Oxide – ∼ 10% of global greenhouse gas emissions ∼ 90% from agriculture –2.5% of Australian national emissions 76% from agriculture in Australia Smith et al. 2007; de Klein & Eckard 2008

Nitrous oxide from cropping and animal production Global Warming Potential –N 2 O = 298 x CO 2 (used in AR4) Note 310 x used in Australian inventory (and AR2) –Long residence time in atmosphere Inert in the troposphere –But absorbs radiation Stratosphere –Cause ozone depletion –Atmospheric concentration 0.3 ppm ( %) IPCC 2007

Nitrous oxide from cropping and animal production Denitrification –Warm, water-logged soils –Excess N in soil Nitrification –Warm, aerobic soils –Minor losses Inefficient use of nitrogen –>60% N lost from grazing –>30% N lost from cropping Eckard 2011

Nitrous oxide from cropping and animal production DCCEE % 4% 6% 26% 5% 41% 25% 17% [ Sources of N 2 O and % contribution

Nitrous oxide from cropping and animal production Factors affecting nitrous oxide formation in soils –N (NO 3 ) –Soil Temperature –Soluble C –Soil pH –Anaerobicity Granli & Bøckman 1994

Nitrous oxide measurement Measurement of N 2 O –Manual and automatic chambers

Nitrous oxide measurement Measurement of N 2 O –Micrometeorological methods

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