Biomass definition is changing often and published by many different institutions providing unclear view. Slight differences couse classification issues but the following definitions present the most important features. There are different definitions of biomass depending of the context (forestry, waste, energy, etc.)

United Nations Framework Convention on Climate Change (UNFCCC):
“The biomass is the non-fossil fraction of an industrial or municipalwaste.”

Organisation for Economic Co-operation and Development (OECD):
"Biomass is defined as any plant matter used directly as fuel or converted into other forms before combustion."

Renewable energy directive, European Commission:"The biodegradable fraction of products, wastes, and residues from biological origin from agriculture (including vegetable and animal substances), forestry, and related industries including fisheries and aquaculture, as well as the biodegradable fraction of industrial and municipal waste"

CEN/TS 14588
The term biomass is defined as material of biological origin excluding material embedded in geological formations and transformed to fossil. BIOfuels means fuels produced directly or indirectly from biomass and bioenergy denotes energy form biofuels

The figure describes the bioenergy utilisation chain from sources of biomass, to biofuel production to final use of bioenergy (CEN/TS 14588).

Standards for "Solid biofuels" produced from biomass.

"Solid biofuels are fuels produced from biomass"; this apparently simple sentence has a deeper significance, since for the most people terms like "pellet" or "chips" are closer to terms like "green, natural, plants, wood" .

Gasoline or diesel fuels sold anywhere in the world are consistent with specific standards, EN 2287 and EN 5908 respectively, stating their chemical and physical characteristics. Fuels not compliant with these standards simply cannot be put onto the market. A simple consequence of this is that, car manufacturers’ guarantees are only valid if a standard fuel is used. More serious consequences are related to the safe use of such fuels or, from an economic point of view, their market price in relation to energy content. For these and other reasons nobody in Europe uses fuels which don’t comply with the standards.

The main standards in the area of biomass fuels are the EN 14961 series. These documents are, at the moment, the unique European Standards dealing with solid biofuel specifications, and, even if they refer to biofuels for non industrial use11 (as stated in their titles), they could also be used as a reference for industrial uses while waiting for more specific standards. An overview of these standards is given in the box below:

Major traded forms of solid biofuels (Source EN 14961-1

EN 14961 - 1 Solid biofuels. Part 1: General requirements.
This European Standard determines the fuel quality classes and specifications for solid biofuels. According to the mandate given for the standardisation work, the scope of the CEN/TC 335 only includes solid biofuels originating from the following sources:
a) products from agriculture and forestry;
b) vegetable waste from agriculture and forestry;
c) vegetable waste from the food processing industry;
d) wood waste, with the exception of wood waste which can contain halogenated organic compounds or heavy metals as a result of treatment with wood preservatives or coating, and which includes in particular such wood waste originated from construction and demolition waste;
e) fibrous vegetable waste from virgin pulp production and from production of paper from pulp, if it is co-incinerated at the place of production and heat generated is recovered;
f) cork waste.

EN 14961 - 2 Solid biofuels. Part 2: Wood pellets for non-industrial use.
This European standard determines the fuel quality classes and specifications of wood pellets for non-industrial use. This European standard covers only wood pellets produced from the following raw materials: Forest, plantation and other virgin wood; By-products and residues from wood processing industry; Used wood.

EN 14961 - 3 Solid biofuels. Part 3: Wood briquettes for non-industrial use.
This European standard determines the fuel quality classes and specifications of wood briquettes for non-industrial use. This European standard covers only wood briquettes produced from the following raw materials: Forest, plantation and other virgin wood; By-products and residues from wood processing industry; Used wood.

EN 14961 - 4 Solid biofuels. Part 4: Wood chips for non-industrial use.
This European standard determines the fuel quality classes and specifications for non-industrial wood chips. This European standard covers only wood chip produced from the following raw materials: Forest, plantation and other virgin wood; By-products and residues from wood processing industry; Used wood.

EN 14961 - 5 Solid biofuels. Part 5: Firewood for non-industrial use.
This European standard determines the fuel quality classes and specifications for firewood for non-industrial use. This European standard covers only firewood produced from the following raw material: Whole trees without roots; Chemically untreated wood residues; Stem wood; Logging residues (thick branches, tops, etc.).

EN 14961 - 6 Solid biofuels. Part 6: Non woody pellets for non-industrial use.
This European Standard determines the fuel quality classes and specifications of non woody pellets for non-industrial use. This European Standard covers only non-woody pellets produced from herbaceous biomass, fruit biomass and their blends and mixtures. Herbaceous biomass is from plants that have a non-woody stem and which die back at the end of the growing season. It includes grains or seeds crops from food processing industry and their by-products such as cereals. Blends are intentionally mixed biofuels, whereas mixtures are unintentionally mixed biofuels.