Carbon calculator

Introduction

The Carbon Calculator is a tool to assess greenhouse gas (GHG) emissions from farming practices and mitigation potential at farm scale. The Carbon Calculator reports the carbon footprint at the farm scale and for the main products of the farm. Mitigation actions are evaluated according to their GHG profile. The tool will also allow comparing emissions from farming practices among similar farms. However, the current version of the Carbon Calculator does not include any database for comparison yet. At this time, there are no usable results in the literature because the methodology used in existing tools always differs from the Carbon Calculator’s methodology. A kind of GHG label has been created, at the farm scale and for the five main products of the farm.

The Carbon Calculator assessment has to be carried out at farm level over a reporting period of one year. The Carbon Calculator takes direct and indirect activities and associated GHG impacts into account. The Carbon Calculator uses a “cradle to farm-gate” approach including:

direct emissions on the site/farm: emissions for energy used, CH4 and N2O (livestock, soils), C storage variations (soil, land use changes, farmland features like trees and hedges) and HFC emissions
indirect emissions (downstream emissions, not on the site) from:
1. agricultural inputs,
2. end-of-life of plastics and organic matter output as waste, and
3. NH3 volatilisation, leaching and run-off (N2O).

The Carbon Calculator does not include emissions out of farm-gate and up to trailers and consumers: distribution, storage by industries, transportation of farm products, and processing out of the farm.

Description of the innovation

Beef	Parameters	Time needed	Complexity	Complete by	Cost
✓	Tier 2			a wide range of people	Freely available

What makes this tool different in comparison with other tools?
The tool reports the GHG emissions avoided thanks to mitigation and sequestration actions.

Enteric fermentation
The general methodology used for emissions from livestock is a Tier 2 simplified method based on the 2006 IPPC Guidelines for national greenhouse gas inventories and adapted for a GHG assessment at farm level.

The rate of methane emissions depends on diet (DMI/day), gross energy (MJ/day), and a methane conversion factor per animal and type of diet.

CH_4enteric = DMI x Y_m x (18.45/55.65)

Where:
CH_4enteric: quantity of methane for one animal, kg.day-1
DMI: dry matter intake, kg.day-1
18.45: mean energy content, of dry matter intake, MJ.kg-1
Y_m: methane conversion factor, %, specific for each livestock category
55.65: energy conversion of methane, MJ.kg-1

CH4 emissions from the different categories of livestock are then summed-up to obtain total annual CH4 emissions from enteric fermentation on the farm. Methane conversion factors depend on husbandry practices: specific live weight, daily dry matter intake and type of diet. The FAO (2010) methodology uses the digestible energy of the diet for cattle and other ruminants. The user has the possibility to choose between different types of digestibility for each type of forage. Generally, data on daily feed intake is not easily available, particularly for grazing livestock. Dry matter intake depends on body weight, feed digestibility or dietary net energy concentration (2006 IPCC- p10.22) and type of animals. The calculation of dry matter intake depends on livestock category and diet types.

Manure management

Methane

Emissions depend on type of manure (solid manure, liquid manure, management and treatment), the organic matter excreted by livestock category and the methane potential by livestock. The calculation is based on:

Volatile solids are the organic material in livestock manure and consist of both biodegradable and non-biodegradable fractions. It is based on DMI, GE, the conversion factor for dietary GE, %DE, urinary energy, and %ashes (8% for cattle)
Number of living days in a year
Maximum methane-producing capacity of the manure (0.18 m³/kg VS for cattle)
Methane conversion factor depends on the type of manure management and the temperature. 17 manure management systems are defined in the tool.

Nitrous oxide

Direct N₂O emissions depend on several factors: N excretion per head and by animal category, % manure management system for each category, and EF for each manure management system.

Direct N2O emissions from manure management depend on the amount of animal manure, sewage sludge, compost, other organic amendments (rendering waste, guano, brewery waste) applied to soils. The calculation of nitrogen applied is considered after building and storage. The emission factor provided for manure application and organic amendment is 1%.

Indirect N₂O emissions are calculated by livestock category, type of manure management system, and N volatilisation for each one. The reduction of NH₃ emissions through crust cover from liquid manure or slurry has been estimated based on the GAINS database. For all animal categories, the reduction of NH₃ emissions is 50 percent.

C sequestration
Soil carbon inventories include estimates of soil organic C stock changes for mineral soils and CO₂ emissions from organic soils due to enhanced microbial decomposition caused by drainage and associated management activity. Carbon stock in trees, hedgerows, vineyards or orchards is taken into account as well as the annual increase of carbon storage in each category.

Mineral soils

Mineral soils are a carbon pool that is influenced by land-use and management activities. For mineral soils, the default method evaluates changes in soil carbon stocks over a finite period of time. The change is computed based on C stock after the management change relative to the carbon stock in a reference condition (i.e., native vegetation that is not degraded or improved). In additionthe , following parameters are included: soil organic carbon in the humus layer from 0 to 30 cm, stock change factor for land-use systems or sub-systems for a particular land-use, and stock change factor for input or organic matter.

Cultivated organic soils

Considerable amounts of organic matter can accumulate over time. Carbon stored in organic soils will readily decompose when conditions become aerobic following soil drainage. Drainage is a practice used in agriculture to improve site conditions for plant growth. Loss rates vary by climate, with drainage under warmer conditions leading to faster decomposition rates. The basic methodology for estimating C emissions from organic soils is to assign an annual emission factor that estimates C losses following drainage. The area of drained and managed organic soils under each climate type is multiplied by the corresponding emission factor to derive an estimate of annual CO2 emissions.

Impact on farm performance

Socio-economic resilience: The tool is free to use
Animal health and welfare: AH&W are not included in this tool
Production efficiency and meat quality: PE&MQ are not included in this tool, only parameters related to dairy cattle
Environmental sustainability: The tool assesses GHG emissions from farming practices and to suggest climate change mitigation and sequestration actions at farm level.