2nd International Conference on Renewable Energy Gas Technology
Barcelona, Spain 2015
Towards a measurement infrastructure for the conformity assessment
of biomethane and upgraded biogas
Adriaan M.H. van der Veen1 and Jianrong Li1
1
Chemistry Group, Van Swinden Laboratorium, Thijsseweg 11, 2629 JA, Delft, the Netherlands
1. Introduction
The
Renewable
Energy
Directive
2009/28/EC [1] establishes a framework
for the promotion of energy from
renewable sources, thus reducing CO2
emissions and securing the supply of
energy in the European Union. In its clause
(2) [1], the use of renewable energy in the
transport sector is referred to as a means
to reduce the EU's dependence on fossil
fuels. Furthermore, in clause (57) [1] the
need to integrate renewable energy into
existing transmission and distribution grids
is stated. The use of agricultural material
[1, clause (12)] is identified as having a
high potential for greenhouse gas
emission reduction and for having
significant environmental advantages at
the same time.
To promote the use of biomethane as
required by 2003/55/EC [4], the properties
of biomethane / biogas need to be
specified. Through mandate M/475 [3],
the European Commission has mandated
CEN, the European Organisation for
Standardisation, to draw up such
specifications for biomethane for injection
into the natural gas transport and
distribution grids and for use as transport
fuels. Access to the natural gas grids is
essential for the promotion of biomethane
and shall not be discriminatory [1, article
16]. In this respect, the Renewable Energy
Directive supplements the requirements in
directive 2003/55/EC [4].
2. Specifications
The feed stocks used for producing biogas
differ substantially, as do the processes for
producing the biogas and upgrading it to
biomethane. The diversity of the feed
stocks used to produce biogas means that
a larger number of parameters than for
natural gas need to be specified, in
particular with respect to critical
impurities. Draft specifications for
biomethane for injection into natural gas
grids [5] and as automotive fuel [6] are
underway. Meeting these specifications is
crucial for the integrity of piping networks,
metering equipment, and of the endusers’ appliances.
Once finalised, these specifications need
to be implemented. The producers of
biomethane and upgraded biogas are
responsible for demonstrating that their
product meets the specifications. On the
other hand, the natural gas grid owners as
well as the operators of refuelling stations
should accept this green gas.
3. Measurement methods and reference
materials
Demonstrating that biomethane and
upgraded biogas meets the specifications
[5,6] requires, among others, reliable
measurement and test methods of known
performance. As a first step towards
developing these methods, reference
methods are developed in the project
“Metrology for Biogas” in the European
Metrology Research Programme (EMRP).
These methods are in turn used to
develop measurement standards which
enable the production and dissemination
of calibration gas mixtures (CGMs) and
certified reference materials (CRMs) for
calibrating instruments used in monitoring
the biogas specifications.
The objectives of the project are aims to
develop and validate methods for
determining key impurities, moisture,
particulates, calorific value, and density:
‒ novel traceable methods for the
measurement of the contents of
key trace-level impurities in biogas
and biomethane namely: total
silicon and siloxanes, sulphurcontaining compounds, aromatic
hydrocarbons,
halogenated
hydrocarbons, ammonia, hydrogen
cyanide, hydrogen chloride and
carbon monoxide.
‒ robust analytical capabilities for
the
measurement
of
the
particulate content and water
content / dew point of biogas and
biomethane.
‒ methods for the measurement of
the calorific value, heat capacity,
and density of biogas and
biomethane.
‒ a
traceable
method
for
determining the concentration of
biomethane in samples of blended
biomethane and natural gas.
‒ robust methods for sampling
biogas and biomethane in the field,
and to enable the biogas industry
to perform robust and traceable
quality assessment measurements.
The project consortium is formed by 12
European National Metrology Institutes
and 3 European Universities. It covers vast
array of expertise and competences,
necessary for carrying out the work in a
3 years’ time frame. The project started on
1 June 2014.
4. Conformity assessment
For conformity assessment, some steps
beyond the scope of the aforementioned
project are needed. One of these is to
develop and draft harmonised methods
that enable onsite or offsite measurement
of relevant properties. The frequency with
which such measurements need to take
place is subject to agreement between the
biogas producer and receiver.
In the conformity assessment, the
measurement uncertainty plays an
important role. Measurement uncertainty
is a parameter that informs about the
accuracy (quality) of a measurement
result. It is closely related to the
reproducibility of a method. Measurement
uncertainty is evaluated in accordance
with the GUM [7]. It is, together with the
specification limit and the measured
value, an input necessary to do the
conformity assessment [8].
Another important aspect concerns the
use of appropriate CRMs and CGMs to
ensure that the equipment is duly
calibrated and periodically checked. In
doing so, the equipment provides results
that are free from significant biases, thus
ensuring
that
the
results
are
metrologically traceable. In the natural gas
area, all results used for custody transfer
and
conformity
assessment
are
metrologically traceable to ensure that
they are fit for purpose.
A further issue concerns the sampling of
biogas, in particular for the determination
of the contents of impurities. Many of
these impurities have a tendency to react
or adsorb on surfaces of samplers,
sampling lines, and sample collection
vessels. The activities in the above
mentioned project focus on assessing the
compatibility and suitability of widely used
means for biogas sampling, such as
sampling bags and adsorption tubes.
Effects such as losses, and the
repeatability and reproducibility of results
as a function of the storage time are
studied and a good practice guide will be
developed in due course.
5. Concluding remarks
The project “Metrology for Biogas” is one
of the key steps in implementing the
specifications EN 16723 for biogas and
biomethane. It broadens the array of
measurement methods used in natural gas
custody transfer to address the specific
issues related to the injection of
biomethane and upgraded biogas into
natural gas grids and for use as transport
fuel.
The project serves as a step-up towards
the development of European harmonised
standard test methods for the parameters
in biogas, not covered so far. In this
development, other parties need to have
their say, as the methods developed in the
project “Metrology for Biogas” are
developed for a different purpose and are
optimised for accuracy rather than for
routine conformity assessment of
biomethane and upgraded biogas.
6. References
[1]
Directive 2009/28/EC of the
European Parliament and of the Council
on the promotion of the use of energy
from renewable sources, Brussels, 23 April
2009
[2]
COM (2010) 639, Energy
2020, A strategy for competitive,
sustainable and secure energy
[3]
European
Commission,
Directorate-general for energy, M/475 EN,
Mandate to CEN for standards for
biomethane for use in transport and
injection in natural gas pipelines, Brussels,
8 November 2010
[4]
Directive 2003/55/EC of the
European Parliament and of the Council
concerning the common rules for the
internal market in natural gas, Brussels, 26
June 2003
[5]
European Organization for
Standardization, prEN 16723-1 -- Natural
gas and biomethane for use in transport
and biomethane for injection in the
natural gas network — Part 1:
Specifications for biomethane for injection
in the natural gas network, 2014
[6]
European Organization for
Standardization, prEN 16723-2 -- Natural
gas and biomethane for use in transport
and biomethane for injection in the
natural gas network — Part 2: Automotive
fuel specifications, 2014
[7]
BIPM, IEC, IFCC, ILAC, ISO,
IUPAC, IUPAP, OIML, ``Guide to the
Expression
of
Uncertainty
in
Measurement, JCGM 100:2008, GUM
1995 with minor corrections'', JCGM
100:2008
[8]
BIPM, IEC, IFCC, ILAC, ISO,
IUPAC, IUPAP, OIML, ``Evaluation of
measurement data -- The role of
measurement uncertainty in conformity
assessment'', JCGM 106:2012