Sustainability and fuel quality issues

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The market for solid biomass has been rapidly growing in recent years. Sustainability encompasses social, environmental and economic aspects. Environmental aspects are crucial when it comes to harvesting biomass from forests or agricultural residues from the fields, but also when biomass is transported and converted. Good quality combustion is also required with high efficiency and low emissions (fine dust) to ensure sustainable operations. Social and economic sustainability is about building trust in the supply chain about the quality and price of biomass. Standards play a crucial role in building trust and confidence in this new market.

1.       Sustainability Issues & Certification Systems


Due to the market growth, regulations concerning the sustainability of biomass became more relevant. Society requested proof of sustainability as a licence to produce and use biomass for fuels and energy. As a response to this and anticipating future policy developments, several voluntary (business to business) schemes have been scaled-up or developed.

At the EU level, there are established sustainability criteria for biofuels for transport and other bio liquids, however not for solid biomass. In 2014, the European Commission issued a report on sustainable biomass for heating and cooling, providing non-binding recommendations for sustainability criteria for biomass. The report encompasses present and future policy developments aimed at minimizing negative impacts of biomass use while maximizing the benefits (European Commission, 2014). The Energy Union proposal COM(2015) 80, article 13 requests a new policy for sustainable biomass and biofuels as well as a legislation to ensure that the 2030 EU targets are cost-effectively met.

There is still a lot to be done and to learn in the context of biomass certification. However, even if the principles are not binding yet, businesses adopting them will have better chances of successfully importing into or trading inside the EU.


1.1       What is a Biomass Certification System?

‘’A biomass certification system is an independent seal showing that biomass or biomass-based products satisfy a certain sustainability standard. Certification systems give all those participating in the biomass chain precise information on how to comply with regulations to ensure the result will meet sustainability criteria.’’

The journey towards certification started with responsible businesses joining forces with organizations from civil society in order to agree upon principles for sustainability criteria. With time, this translated into certification systems. Today some certification systems that are recognised only at national level, others at international level. The certification systems can be developed by different parties: NGOs, governments, businesses or associations. Because of this, each certification can emphasise different aspects and interests and can have different scopes and complexities (RVO, 2013). Regardless of this, a certification system has three main elements:

● The sustainability standard;

● The Chain of Custody;

● The rules managing the system.

Depending on the feedstock, the certification systems are classified as follows:

● Forest certification systems;

● Agricultural certification systems;

● General biofuel/bioliquid certification systems;

● Solid biomass for bioenergy certification (RVO, 2013).

1.2       The Certification Management System

For each certification there is a management system that sets out the rules by which it operates. This can include the rules that the govern audits, the level of transparency and accessibility, the level of stakeholder engagement or the way complaints are handled.

In order for a system to be transparent and accessible, information needs to be made readily available. This can include rights and obligations of certified companies, documentation of the certification system, lists with certified companies and assessment reports.

A certain level of stakeholder engagement needs to be assured by making them able to review or evaluate the certification system. Apart from these, the certification system needs to have a responsive complaint system that is easily accessible by anyone.

Audit system rules are very important for the certification system. In this context these refer to aspects such as:

The audit frequency and validity, which determines how often the auditors determine the validity of the certificates;

Audit types which can range from self-declarations to full field audits;

● The audit management which sets out specific procedures and the rules for their execution. This is specified in a standard document against which the auditors evaluate compliance. It is necessary to clearly define the sanctions for non-compliance. This needs to determine how and how soon the failures to meet the standard requirements are to be corrected;

The transparency and accessibility of the system should be achieved by making information publicly available;
Stakeholder involvement needs to be possible during the audit process, in terms of either participating in or observing the audit process;

A complaint system needs to be set in place and to be easily accessed by anyone.

1.3       How to Select a Certification System?

The decision tree below provides a practical guidance to operators in selecting the sustainability certification scheme for solid biomass. It helps an organization deciding which certification scheme is necessary or most appropriate in a particular situation.

Figure 1 – Decision tree for selecting a sustainability certification scheme (NL Agency, 2013, p.30)

2.       Quality of Solid Biomass

2.1       The Importance of Quality Assurance

Biomass is used in bioenergy plants of very different scales, ranging from a few kW to several MW. Solid biofuels can be characterised on the basis of a number of physical and chemical parameters. Depending on the size and type of the combustion system, the requirements which are set for the physical-chemical quality of the biomass might vary. Suppliers of combustion systems incorporate biomass requirements in their boiler specifications. In Figure 5 the most important parameters and their relationship with the operation of a bio-energy system are schematically shown.




Figure 2 – Quality parameters for solid biomass




Quality standards provide several advantages. In addition to the advantage of a better functioning boiler, the biomass end-user can more easily distinguish between different qualities of chips and pellets on the market. Also, quality standards make it easier to analyse possible problems with the combustion system. After all, when the boiler runs on well-specified biomass only, the fuel can be ruled out as a cause of operating problems. In addition, as the biofuel is no longer distinctive, the standard use of good quality biofuels separates the good combustion systems from the lesser ones. Finally quality standards generally provide more confidence in the market. For licensing authorities and regulators quality standards may offer additional guarantees, like the use of biofuels with low (or less) emissions and nuisance. This all contributes to the professionalism of the biomass and bioenergy market.

In smaller systems the quality of biomass is very important, and large fluctuations in the compound and thus quality of biomass are undesirable (especially with wood chips). Larger installations generally have a greater range of wood chip quality which can be easily handled.

In practice, the use of wood chips that do not meet the specifications given by the boiler manufacturer is quite common, especially at smaller bio-energy plants (<1 MW). This creates mechanical problems, problems with the energy yield and / or increased emissions.

Mechanical problems may occur and cause failures when using, for instance, too large pieces of wood that block the fuel supply system. The energy efficiency of the installation decreases when the biomass contains too much moisture or has a low energy content. In addition, too much sand will cause excessive wear of mechanical parts. An indirect consequence of these failures and sub-optimal process management is that they may increase emissions (dust, NOx).

In contrast to wood chips the pellets manufacturer and user rarely are the same person. This means that the pellet user cannot control the pellet quality during production and has to find other ways to ensure the quality of his pellets: the certificate gives a guarantee of quality, and the requirements for the certification are set by standards.


2.2       Quality Standards

At the European level, the European Committee for Standardisation (CEN) and the European Commission are the main responsible bodies for standardization. They are responsible for the policy decisions regarding solid biofuels, quality and sustainability criteria. (NEN, VTT, 2011)

CEN is an organization that works in a decentralised way. Its 32 members – the National Standardization Bodies of the EU27, of 3 EFTA countries and of Croatia and Turkey – operate the technical groups that draw up the standards. Its network comprises more than 60,000 technical experts from the industry, academia, societal organizations or associations.

The standards are voluntary which means that they are not legally binding. However, laws and regulations may refer to standards and even make compliance with them compulsory. (CEN, 2015)

Standards ensure compliance with the recognised EU criteria and provide information to the consumers about the products they buy. It is particularly important to have standards for the bioenergy sector as the quality of the biomass determines the choice of technology for the plant. It also provides support to trade partners by offering them a common jargon, which is necessary for the EU market. (NEN, VTT, 2011)

In order to create an enabling market for the development of solid biofuels it is necessary that policy makers, standardization bodies and industries work together. It is a market that continuously evolves and parties need to keep exchanging feedback in order to keep up with its developments. (NEN, VTT, 2011)

The EU project Solid Standards (see Solid Standards) offers a good overview of the implementation of quality and sustainability standards and certification schemes for solid biofuels. The Recommendation Paper on the development of certification systems for the Solid Standards project gives an overview about the required content of certification schemes for solid biomass, how they should be structured, and what approaches for current schemes other than wood pellets exist. For detailed information please see the main publications here.

To enable different wood fuels to be categorised based on their quality characteristics, various national fuel standards have been developed in recent years. Standards make it possible to describe a fuel more accurately and are useful to both producers and consumers as a means of navigating the fuel market. Until recently, there were only individual national standards for certain types of fuel products such as pellets, wood chips and wood briquettes. The quality of wood chips in Europe, for example, is generally expressed in accordance with the categories and specifications of the Austrian ÖNORM M 7133. Here, the most important parameters are requirements regarding the size of the wood chips, their water content, bulk density and ash content. For pellets there are the Austrian ÖNORM M 7135, the German DIN 51731 and the Italian and French quality marks “PelletGold” and “ITEBE”. In recent years, the European Committee for Standardization (CEN) in its ‘technical committee CEN / TC 335 solid fuels’ developed the so-called EN 14961 standards replacing all national standards. In 2015 the EN 14961 standard has been replaced by EN ISO 17225. The series of standards in EN ISO 17225 provides a uniform, Europe-wide tool for standardizing any fixed fuel that can be used for energy production. The purpose of this standard is to encourage the use of wood fuels and to eliminate trade barriers between European countries. The standard for wood fuels actually consists of three interrelated sets of standards:

  1. A standard which determines the terminology and definitions for solid biofuels, ISO 16559;
  2. Standards for fuel specifications and classes, and the chemical and physical characteristics, EN ISO 17225;
  3. Standards that set how the characteristics of biofuels must be determined (analysis methods, etc.). Examples are EN 14774 for determining the moisture content and EN 14918 for determining the caloric value.

With these three sets of standards the definitions for woody biomass are set and the physical and chemical parameters applicable on woody biomass (quality aspects) – and how those parameters are to be determined – are defined.

2.2.1       Quality Certification for Pellets

Based on the ISO 17,225-2 and the 15,234-2 EN standards for wood pellets, the European certification for wood pellets ENplus has been developed. The ENplus system was developed by the DEPI, the German Pellet Institute. The license rights for the scheme lies within the European Pellet Council (EPC), part of the European Biomass Association (AEBIOM).

The ENplus certification focuses on pellet producers and pellet traders. This sets requirements for the production, transport and storage of pellets. Only when the entire chain is certified, the respective pellets meet the ENplus standard. The ENplus certification scheme consists of several elements:

● Definitions for quality classes pellets and pellet specification of properties;

● Specification of internal quality from producers and traders;

● Manner of quality pellets and quality assurance in the supply chain;

● Requirements for the certification process;

● Conditions for using the ENplus label.

More information can be found in the Handbook for the Certification of Wood Pellets for Heating Purposes [10] at

Wood Pellets are classified in three classes: A1, A2 and B.

Class A1 is the quality pellet for private use. These pellets have the most stringent quality requirements, in particular in relation to the ash content (0.5% for softwood to 0.7% for other types of wood such as oak, beech, birch, meranti, etc.).

Class A2 is the quality with a permitted ash content of maximum 1.5%. For example, this quality is suitable for devices that burn both wood pellets and wood chips, and which are somewhat less critical to the quality of biofuel.

Class B are industrial pellets. These are primarily used in industrial installations such as very large combustion or co-firing in power plants. The above requirements are less stringent than for classes A1 and A2.

More on European pellets standards can be found here.


2.2.2       Quality Certification of Wood Chips

At this moment DEPI is developing a new certification system for woodchips called HackZert. The DEPI system will be designed to work along the lines of the ENplus system that covers wood pellets. In an announcement on 19 February, DEPI said the HackZert project was supported by the German Federal Ministry of Food and Agriculture (BmEL).

The scheme is scheduled to start next year. During the rest of 2015 work will focus on development with different woodchip producers as well as boiler makers and operators.

Another example is the Woodsure Accreditation Scheme, launched in the UK in 2011. It provides a competent and ongoing assessment of fuel providers and assists them to achieve and maintain a high standard of woodfuel. The fuels covered under the accreditation scheme are: woodchip, hog wood (shred), pellets and briquettes. More information can be found on the Woodsure homepage.

The above text is extracted from B4B’s “Sustainability and fuel quality issues” report. Click HERE to download the full version.