Specification

The NORM ROAST protocol allows the standardized assesment of the levels of pollutants, CO2 emissions and energy consumption of small to mid-size batch coffee roasting machines.

Abbreviations

Abbreviation Definition
BT Bean Temperature
FCs First Crack start
DROP Drop at the end of a roast
CF Correction Factor
CV Calorific Value
LPG Propane Gas
NG Natural Gas
Elec Electricity
CO Carbon Monoxide
CO2 Carbon Dioxide
NOx Nitrogen Oxides
SO2 Sulfur Dioxide
PM Particulate Matter

Principle

The total energy consumption and average pollutant concentration in the exhaust air of a roasting machine are measured over a measurement cycle including the pre-heating of the machine from room temperature and 4 roast batches.

Consumption & CO2 Emissions

The energy used to roast one kg of beans is computed from the total energy consumed and the amount of green coffee roasted.

The total CO2 emissions used to roast one kg of unroasted beans is calculated from the energy consumption per energy type (LPG, NG or Elec).

The batch size and other process parameters have to be choosen to meet the requirements of the Roast Profile defined in the document.

Pollutants

The concentrations of pollutants measured in the exhaust air are averaged over the complete test cycle. Calibrated, validated and well maintained instruments have to be applied according to the instructions of their manufacturer and the relevant international standard.

Pollutant Standard
CO2 ISO 12039
CO ISO 12039
NOx ISO 10849
SO2 ISO 7935
PM ISO 9096

Pre-Conditions

Ambient Conditions

During the execution of the test cycle the air in the test room must fullfill the following limits.

Parameter Range
temperature 20 – 30°C
pressure 950 – 1050 hPa

Raw Coffee Beans

The raw coffee beans used in the test cycle have to be washed Arabica with the following properties

Property Range
moisture 10.5 – 11.5%
bulk density 670 – 730 g/l
screen size 17/18 1/64”
temperature 20 – 30°C

Roast Profile

The test roasts have to heat up the coffee beans such that the audible popping sound of first-crack (FCs) occurs 10:00min into the roast and the roast ends (DROP) after 12:30min at a bean temperature by 10°C higher than that at FCs.

Event  Roast Time Bean Temperature
FCs 10:00min tFCs
DROP 12:30min tFCs + 10°C

Measurement Cycle

The full measurement cycle takes about one hour and includes the pre-heating of the machine from room temperature and 4 roast batches that follow the profile specified in the previous section.

The batch size must be the same for each of the 4 roast batches and chosen such that each batch meets the Roast Profile times and temperatures defined above.

The duration of pre-heating, as well as the time and bean temperature at FCs and DROP has to be noted for each batch.

The energy consumption and pollutants are measured over the full cycle. The consumptions are measured separately per energy type (LPG, NG, Elec). The consumptions during pre-heating and the 4 roast batches are noted separately. The consumptions in the period between batches must be fully accounted for in the totals.

The pollutants have to be measured in the exhaust according to the corresponding norm and averaged over the full period.

Calculation

Energy consumption and CO2 emissions are reported per kg of green coffee. Thus the calculated consumption and emission values (pre-heating + roasting 4 batches) are divided by the total amount of raw coffee roasted during the measurement cycle (4 batches). Note that the batch size should be chosen to minimize the consumption per kg and does not need to correspond to the nominal batch size of the machine as indicated by the manufacturer.

Gas consumption is usually measured in volume. The following formulas are used to convert the gas volume to energy consumption in kWh and energy consumption to estimated CO2 emissions.

Note that the measuring cycle starts with the start of the pre-heat process and ends after batch #4 is released from the drum. The total duration of the cylce includes also the time spent between roasting the 4 batches (between batches protocol).

Energy

Given the measured gas volume, the energy consumed calculates as

Energy (kWh) = Volume (m3) x CF x CV (kWh/m3)

with

Constant Name  Description
CF Correction Factor adjusts volume for differences in temperature and pressure per supply [3]
CV Calorific Value gas energy content per volume

CO2

The CO2 emitted per energy consumed calculates as

CO2 (g) = Energy (kWh) * C (g/kWh)

with the factor C as

Type C  Reference
Propane 214.56 g/kWh [1]
NG 180.54 g/kWh [1]
Elec 385.55 g/kWh (*)

(*) : the CO2 emissions for electric energy depends on the clean electric energy mix. To make the results comparable we estimate the CO2 emission by taking the average CO2 emissions across all generation sources in the U.S. for 2020 including carbon neutral sources, which is 0.85 pounds of CO2 per kWh (385.55 g/kWh) [2]. For specific countries or utilities where carbon neutral sources are greater the actual figure could be significantly lower.

Report

The test cycle has to be fully documented by filling the following form.

NORM ROAST Consumption & Emissions Form

A filled-out example of that form is provided here.

NORM ROAST Consumption & Emissions Form

Additionally, supporting measuring protocols, like roast, emissions and consumption logs should be provided.

References

[1] Carbon Dioxide Emissions Coefficients, U.S. Energy Information Administration, Nov. 18, 2021
[2] How much carbon dioxide is produced per kilowatthour of U.S. electricity generation?, U.S. Energy Information Administration, referencing data from 2020