oSIST prEN 17983:2023
(Main)Algae and algae products - Measurement for renewable algal raw material for energy and non-energy applications
Algae and algae products - Measurement for renewable algal raw material for energy and non-energy applications
This document specifies the methods to be used for the measurement of energy content and main elements balances of algae from cultivation or from wild growth and algae products to provide biomass, intended for renewable algal raw material used as bioenergy and in bio-based products.
This document does not apply to methods of algae and algae products sampling, harvesting and pre/postprocessing.
This document does not apply to algae and algae products intended for the food and feed sector.
Algen und Algenprodukte - Charakterisierung nachwachsender Algenrohmaterialien für Energie- und Nichtenergieanwendungen
Dieses Dokument legt die Verfahren fest, die zur Messung des Energiegehaltes und Bilanzierung der Hauptbestandteile von kultivierten oder wild aufgezogenen Algen und Algenprodukten, die Biomasse liefern und für erneuerbares Algen Ausgangsmaterial zur Verwendung als Bioenergie und biobasierte Produkte vorgesehen sind, anzuwenden sind.
Dieses Dokument gilt nicht für Verfahren der Probenahme, Ernte und Vor /Nachverarbeitung von Algen und Algenprodukten.
Dieses Dokument gilt nicht für Algen und Algenprodukte, die für die Lebensmittel und Futtermittelindustrie vorgesehen sind.
Algues et produits à base d’algues - Mesure de la matière première algale renouvelable pour les applications énergétiques et non énergétiques
No Scope Available
Alge in izdelki iz alg - Merjenje obnovljivih surovin iz alg za energetske in neenergetske namene
General Information
Standards Content (Sample)
SLOVENSKI STANDARD
oSIST prEN 17983:2023
01-julij-2023
Alge in izdelki iz alg - Merjenje obnovljivih surovin iz alg za energetske in
neenergetske namene
Algae and algae products - Measurement for renewable algal raw material for energy
and non-energy applications
Algen und Algenprodukte - Charakterisierung nachwachsender Algenrohmaterialien für
Energie- und Nichtenergieanwendungen
Ta slovenski standard je istoveten z: prEN 17983
ICS:
13.020.55 Biološki izdelki Biobased products
oSIST prEN 17983:2023 en,fr,de
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.
---------------------- Page: 1 ----------------------
oSIST prEN 17983:2023
---------------------- Page: 2 ----------------------
oSIST prEN 17983:2023
DRAFT
EUROPEAN STANDARD
prEN 17983
NORME EUROPÉENNE
EUROPÄISCHE NORM
May 2023
ICS 13.020.55
English Version
Algae and algae products - Measurement for renewable
algal raw material for energy and non- energy applications
Algen und Algenprodukte - Charakterisierung
nachwachsender Algenrohmaterialien für Energie- und
Nichtenergieanwendungen
This draft European Standard is submitted to CEN members for enquiry. It has been drawn up by the Technical Committee
CEN/TC 454.
If this draft becomes a European Standard, CEN members are bound to comply with the CEN/CENELEC Internal Regulations
which stipulate the conditions for giving this European Standard the status of a national standard without any alteration.
This draft European Standard was established by CEN in three official versions (English, French, German). A version in any other
language made by translation under the responsibility of a CEN member into its own language and notified to the CEN-CENELEC
Management Centre has the same status as the official versions.
CEN members are the national standards bodies of Austria, Belgium, Bulgaria, Croatia, Cyprus, Czech Republic, Denmark, Estonia,
Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway,
Poland, Portugal, Republic of North Macedonia, Romania, Serbia, Slovakia, Slovenia, Spain, Sweden, Switzerland, Türkiye and
United Kingdom.
Recipients of this draft are invited to submit, with their comments, notification of any relevant patent rights of which they are
aware and to provide supporting documentation.
Warning : This document is not a European Standard. It is distributed for review and comments. It is subject to change without
notice and shall not be referred to as a European Standard.
EUROPEAN COMMITTEE FOR STANDARDIZATION
COMITÉ EUROPÉEN DE NORMALISATION
EUROPÄISCHES KOMITEE FÜR NORMUNG
CEN-CENELEC Management Centre: Rue de la Science 23, B-1040 Brussels
© 2023 CEN All rights of exploitation in any form and by any means reserved Ref. No. prEN 17983:2023 E
worldwide for CEN national Members.
---------------------- Page: 3 ----------------------
oSIST prEN 17983:2023
prEN 17983:2023(E)
Contents Page
European foreword . 3
Introduction . 4
1 Scope . 5
2 Normative references . 5
3 Terms and definitions . 5
4 Measurement for renewable algal raw material . 9
4.1 General. 9
4.2 Energy balance of algae facilities and algae products for Life Cycle Assessment and
Techno-Economic Analysis . 11
4.3 Mass balance of main algal biomass elements . 15
4.4 Parameters specific to algae as bio-based products . 21
4.5 Water management . 23
4.6 Air management . 25
Annex A (informative) Example of calculation for the measurement of energy and main
elements balances of algae systems . 26
A.1 Energy . 26
A.2 Carbon . 26
A.3 Nitrogen . 26
Annex B (informative) Overview on carbon/CO neutrality . 27
2
Annex C (informative) Overview on life cycle assessment (LCA) . 28
C.1 General. 28
C.2 Existing standards for LCA . 28
C.3 Relation between present document and EN 16760 . 28
C.4 Applications of LCA to algae biomass production . 28
Annex D (informative) Algae as feedstocks for biofuels . 30
Bibliography . 31
2
---------------------- Page: 4 ----------------------
oSIST prEN 17983:2023
prEN 17983:2023 (E)
European foreword
This document (prEN 17983:2023) has been prepared by Technical Committee CEN/TC 454 “Algae and
algae products”, the secretariat of which is held by NEN.
This document is currently submitted to the CEN Enquiry.
This document has been prepared under a Standardization Request given to CEN by the European
Commission and the European Free Trade Association.
3
---------------------- Page: 5 ----------------------
oSIST prEN 17983:2023
prEN 17983:2023(E)
Introduction
This document has been prepared by the experts of CEN/TC 454 “Algae and algae products”.
The European Committee for Standardization (CEN) was requested by the European Commission (EC)
to draft European standards or European Standardization deliverables to support the implementation
of Article 3 of Directive 2009/28/EC for algae and algae-based products or intermediates.
This request, presented as Mandate M/547, also contributes to the Communication on “Innovating for
Sustainable Growth: A Bio economy for Europe”.
The former working group CEN Technical Board Working Group 218 “Algae” was created in 2016 to
develop a work program as part of this Mandate. The technical committee CEN/TC 454 “Algae and algae
products” was established to carry out the work program that will prepare a series of standards.
The interest in algae and algae-based products or intermediates has increased significantly in Europe as
a valuable source of, including but not limited to, carbohydrates, proteins, lipids, and several pigments.
These materials are suitable for use in a wide range of applications from food and feed purposes to
other sectors, such as textile, cosmetics, biopolymers, biofuel and fertilizer/biostimulants.
Standardization was identified as having an important role in promoting the use of algae and algae
products.
The work of CEN/TC 454 should improve the reliability of the supply chain, thereby improving the
confidence of industry and consumers in algae, which include macroalgae, microalgae, cyanobacteria,
Labyrinthulomycetes, algae-based products or intermediates and will promote and support
commercialization of the European algae industry.
In industrial and scientific assessments, many methodological differences occur with regard to mass
and energy balances. This constitutes a major issue, as the results often are difficult to compare.
The goal of this document is to define basic metrics for carbon accounting of algae, so as to allow a more
scientifically sound comparison between algae systems and other biomass feedstocks.
The need for such metrics and methodology is related to the wide existing differences in algae growth
sites and strategies. For example, there are significant differences in the application of the “green box
concept” to closed cultivation units and wild harvested algae. However, common sustainability and life-
cycle-analysis (LCA) approaches are needed.
These metrics can be used to apply existing LCA standards to algae systems.
Clarifications, considerations, practices, simplifications and options for the different LCA applications
are beyond the scope of this document. This document may be applied in studies that do not cover the
whole life cycle, such as cradle-to-gate studies, e.g. algal biomass farming or wild collection. The
downstream processes, generally referred to as “biorefining”, are not covered since it is deemed to be
equivalent to plant biomass. An overview of LCA standards is given in Annex C.
This document aims to provide specific life cycle assessment requirements and guidance for algae
cultivation, based on EN ISO 14040 Environmental management – Life cycle assessment – Principles and
framework, EN ISO 14044 Environmental management – Life cycle assessment – Requirements and
guidelines and EN 16760 Bio-based products – Life Cycle Assessment. These standards are all applicable
to algae-based products, but the topic which is not clearly defined in these standards is the accounting
of the main parameters of algae cultivation sites. The sustainability aspects of algae cultivation can be
assessed either by EN 16751, Bio-based products – Sustainability criteria when the outcome is a product,
or by ISO 13065, when the outcome is energy. Both these documents provide a framework for
considering environmental, social and economic aspects that can be used to facilitate the evaluation and
comparability of biomass for products or energy, respectively.
With EN 16785-1 Bio-based products – Bio-based content – Part 1: Determination of the bio-based
content using the radiocarbon analysis and elemental analysis application to algae the problem of fossil
CO as photosynthesis feed arises which calls for proper application criteria opposite to plant
2
photosynthesis. A similar situation can arise for nitrogen and phosphorus capture in open seas.
4
---------------------- Page: 6 ----------------------
oSIST prEN 17983:2023
prEN 17983:2023 (E)
1 Scope
This document specifies the methods to be used for the measurement of energy content and main
elements balances of algae from cultivation or from wild growth and algae products to provide biomass,
intended for renewable algal raw material used as bioenergy and in bio-based products.
This document does not apply to methods of algae and algae products sampling, harvesting and
pre/postprocessing.
This document does not apply to algae and algae products intended for the food and feed sector.
2 Normative references
The following documents are referred to in the text in such a way that some or all of their content
constitutes requirements of this document. For dated references, only the edition cited applies. For
undated references, the latest edition of the referenced document (including any amendments) applies.
EN 14268, Irrigation techniques - Meters for irrigation water
EN 17399, Algae and algae products - Terms and definitions
EN 17480, Algae and algae products - Methods for the determination of productivity of algae growth sites
EN 17605, Algae and algae products - Methods of sampling and analysis - Sample treatment
EN ISO 4064-1, Water meters for cold potable water and hot water - Part 1: Metrological and technical
requirements (ISO 4064-1)
EN ISO 18125, Solid biofuels - Determination of calorific value (ISO 18125)
3 Terms and definitions
For the purposes of this document, the terms and definitions given in EN 17399, EN 17480, EN 17605
and the following apply.
ISO and IEC maintain terminology databases for use in standardization at the following addresses:
— ISO Online browsing platform: available at https://www.iso.org/obp/
— IEC Electropedia: available at https://www.electropedia.org/
3.1
biomass dry matter
material remaining after removal of moisture under specific conditions
[SOURCE: EN ISO 16559:2022 3.71 – modified, biomass added to the term]
3.2
moisture content
loss on drying
ratio of algae sample mass lost after drying under test conditions till constant weight and initial mass
3.3
biomass ash content
mass of microalgae and macroalgae residue remaining after the sample is placed in a muffle furnace at a
temperature of (575 ± 10) °C
5
---------------------- Page: 7 ----------------------
oSIST prEN 17983:2023
prEN 17983:2023(E)
3.4
illumination
exposition to light from other sources than sun
3.5
photosynthetic production area
insolated horizontal surface of the cultivation unit where photosynthesis is driven by natural light in
natural basins, natural sites and insolated ponds
Note 1 to entry: The production area of non-horizontal systems results in multi-interpretable outcomes;
therefore, non-horizontal systems use the volume productivity formula to calculate productivity.
Note 2 to entry: Wild growth areas are excluded.
Note 3 to entry: Systems that use illumination (see 3.11) use volume productivity formula to calculate
productivity.
3.6
algae growth site area
area of a single or multiple algae cultivation unit(s)or natural sites, including auxiliary equipment
needed to operate the unit and service area
Note 1 to entry: Cultivation unit area includes ponds, bubble columns, tubular photobioreactors, green-wall
panels or any kind of devices utilized to grow algae, and all the equipment, tubing and connections necessary for
the specific unit to function (e.g. the area occupied by the pumps and recirculating reservoir/ degasser in a tubular
photobioreactor), and the service area around. If the service area is not clearly defined, it is by default 1 m all
around the cultivation unit.
Note 2 to entry: Cultivation unit area does not include equipment upstream and downstream of the cultivation
unit, e.g. the reservoirs for water preparation and/or harvesting.
Note 3 to entry: The specification of the area in a wild growth site where macroalgae are growing in nature
without human interference, except when harvesting, is misleading for the calculation of productivity as many
factors influence the growth (e.g. currents, mixture of species, natural regeneration cycles, etc.). For an
investigation on the productivity and its sustainability of an aquatic ecosystem an area estimation is possible, but
this exceeds the scope of this document.
3.7
total carbon
TC
quantity of carbon present in a product in the form of organic, inorganic and elemental carbon
[SOURCE: EN 16575:2014, 2.17]
6
---------------------- Page: 8 ----------------------
oSIST prEN 17983:2023
prEN 17983:2023 (E)
3.8
dissolved inorganic carbon
DIC
carbon dissolved in water in inorganic form as carbonates and bicarbonates in equilibrium with
gaseous dissolved CO
2
Note 1 to entry: Dissolved CO2 molecules are notated CO2aq.
3.9
dissolved organic carbon
DOC
carbon dissolved in water in organic molecules
Note 1 to entry: Glycerol, acetic acid and sugar are examples of DOC molecules.
3.10
carbon accounting
evaluation of carbon-containing mass flows transferred from inputs to biomass in algae cultivation for
sustainability and/or credit claims
3.11
bio-based product
product wholly or partly derived from biomass
Note 1 to entry: The bio-based product is normally characterized by the bio-based carbon content or the bio-
based content. For the determination and declaration of the bio-based content and the bio-based carbon content,
see the relevant standards of CEN/TC 411.
Note 2 to entry: Product can be an intermediate, material, semifinished or final product.
Note 3 to entry: “Bio-based product” is often used to refer to a product which is partly bio-based. In these cases,
the claim should be accompanied by a quantification of the bio-based content.
[SOURCE: EN 16575:2014, 2.5]
3.12
carbon footprint
CFP
sum of GHG emissions and GHG removals in a product system, expressed as CO equivalents and based
2
on a life cycle assessment using the single impact category of climate change
[SOURCE: EN ISO 14067:2018, 3.1.1.1 – modified. Note 1 and 2 to entry omitted]
3.13
greenhouse gas
GHG
gaseous constituent of the atmosphere, both natural and anthropogenic, that absorbs and emits
radiation at specific wavelengths within the spectrum of infrared radiation emitted by the earth’s
surface, the atmosphere, and clouds
[SOURCE: EN ISO 14067:2018, 3.1.2.1 – modified. Note 1 and 2 to entry omitted]
7
---------------------- Page: 9 ----------------------
oSIST prEN 17983:2023
prEN 17983:2023(E)
3.14
flue gas
gases produced by combustion of a fuel that are normally emitted to the atmosphere
Note 1 to entry: Flue gas from combustion processes exploited for other purposes than CO2 production are
examples of flue gas, e.g. power plants CO2 emissions.
[SOURCE: ISO/TR 27912:2016, 3.31 – modified. Note 1 to entry added]
3.15
cryogenic CO
2
liquid CO stored and transported as industrial product
2
3.16
biogenic CO
2
carbon dioxide generated from the combustion or degradation of biogenic carbon (biobased carbon)
(3.25)
3.17
carbon neutral CO
2
carbon dioxide generated as byproduct or waste, after its carbon footprint is fully cleared over the
production system
Note 1 to entry: Examples of this carbon dioxide are flue gas from combustion of fossil fuels for energy
production, roasting of carbonates, steam reforming of natural gas, as far as the CFP (carbon footprint) of these
sources are completely accounted for over the main product, e.g. electric power, calcium oxide, hydrogen.
Note 2 to entry: An overview on carbon/CO neutrality is reported in Annex B.
2
3.18
open land-based cultivation
controlled growth cultivation performed on land without totally controlled mass flow referring to all
solid and liquid mass flows which enter or exit the system without passing a measurable section, e.g.
unlined pond
3.19
closed cultivation
controlled growth cultivation performed with controlled mass flow
Note 1 to entry: Uncontrolled gaseous mass flow from/to atmosphere is possible, e.g. CO absorption and/or O
2 2
release and water vapor release.
Note 2 to entry: Open ponds without bottom liner including natural basins are not considered as closed
cultivation systems.
3.20
open water
aqueous environment where algae exchange elements without controlled mass flow
3.21
photosynthetic system
algae cultivation based on phototrophy as defined in EN 17399
8
---------------------- Page: 10 ----------------------
oSIST prEN 17983:2023
prEN 17983:2023 (E)
3.22
mixotrophic system
algae cultivation based on mixotrophy or photoheterotrophy as defined in EN 17399
3.23
heterotrophic system
algae cultivation based on heterotrophy as defined in EN 17399
3.24
biomass
material of biological origin excluding material embedded in geological formations and/or fossilized
EXAMPLES (Whole or parts of) plants, trees, algae, marine organisms, microorganisms, animals, etc.
[SOURCE: EN 16575:2014]
3.25
bio-based carbon
biogenic carbon
carbon derived from biomass
Note 1 to entry: Biogenic carbon is defined in EN ISO 14067:2018, by the same definition.
[SOURCE: EN 16575:2014, 2.2 – modified. Note 1 to entry updated]
3.26
photosynthetic conversion efficiency
η
ratio between energy content of algae biomass and energy inputs to phototrophic algae cultivation
Note 1 to entry: The photosynthetic efficiency is the fraction of light energy (photons) converted into algae
chemical energy during phototrophic algae cultivation. The ratio between energy content of the grown algae
biomass and energy needed to cultivate them is the efficiency.
4 Measurement for renewable algal raw material
4.1 General
4.1.1 General
The measurement for renewable algal raw material can be carried out by means of the “Green Box”
approach [1], see Figure 1. It describes the industry’s environmental, economic, and carbon footprint
via quantifying the inputs and outputs of an algae growth site. These input/output measurements
systematically allow for economic projections (through techno-economic analyses) and sustainability
calculations (through life cycle assessments).
4.1.2 Green box inputs and outputs
Inputs may include the carbon, water, energy, and nutrients required by the algae, as well as land
requirements, process consumables, and human resources required by the infrastructure. Green Box
outputs include the different classes of algal products as well as industrial waste emissions including
gas, liquid, and solid discharges.
Together, the measured inputs and outputs generically carve out the total economic and environmental
footprint of any algal operation. Identifying this total footprint is central in the technical and
9
---------------------- Page: 11 ----------------------
oSIST prEN 17983:2023
prEN 17983:2023(E)
sustainability review of an expanding algae industry. For sample treatment of algae and algae products
see EN 17605.
Figure 1 — Green box for the measurement of renewable algal raw material
4.1.3 Green box boundaries
The boundaries for algae production are limited by the Green Box approach where it accounts for one
year production or other relevant operative time in natural sites, open land-based cultivation, and
closed cultivation.
These production pathways need to be separately considered as in natural sites, water, carbon,
nutrients inputs and energy, gas and liquid emissions are not measured. In open land-based cultivation,
liquid streams in not-controlled flow are present (leakage from unlined ponds, spreading in agriculture,
etc.) which cannot be measured. In closed cultivation all mass flow is controlled and can be measured
except CO and O release/absorption from atmosphere. In the same way, all other non-controlled gas
2 2
exchange (diffusion) from algae to atmosphere can happen and is neglected (e.g. ammonia release, etc.).
Examples of the processes are shown in Figure 2, Figure 3 and Figure 4.
In all the cases, infrastructure (e.g. facility capex and component materials) shall be considered (see
EN ISO 14064-1). Infrastructure can be referred to as its amortization figures (e.g. measured in
€/(time∗kg) units and component materials weight divided by life time.
When there are other bio-products as outputs or associated energy production, system can be
subdivided or expanded to include the additional impacts related to the co-products or allocation
concept should be considered (EN ISO 14044). The environmental impact can be allocated to the
products (outputs of the Green Box) by weight, energy, or economic value.
Figure 2 — Green box boundaries for natural sites
10
---------------------- Page: 12 ----------------------
oSIST prEN 17983:2023
prEN 17983:2023 (E)
Figure 3 — Green box boundaries for open land-based cultivation
In open land-based cultivation liquid streams in not-controlled flow are present (leakage from unlined
ponds, spreading in agriculture, etc.) which cannot be measured.
Figure 4 — Green box boundaries for closed cultivation
In closed cultivation all mass flow is controlled and can be measured except CO absorption/release
2
from atmosphere and O release/absorption from atmosphere. In the same way, all other non
2
controlled gas exchange (diffusion) from algae to atmosphere can happen and is neglected, e.g.
ammonia release, etc.
4.2 Energy balance of algae facilities and algae products for Life Cycle Assessment and
Techno-Economic Analysis
4.2.1 General
Energy includes all flows measurable in kWh/yr (or kW), if any, e.g. the output of a biogas digestor +
power station included in the algae facility, or e.g. the energy value (combustion heat) of biomass; and
11
---------------------- Page: 13 ----------------------
oSIST prEN 17983:2023
prEN 17983:2023(E)
all energy input consumed to perform cultivation, related to the production of the functional unit (i.e.
1 kg of algae).
4.2.2 Energy inputs and outputs
Figure 5 provides an overview of all energy input and output for land based cultivation which holds
both for open and closed systems.
Figure 5 — Overview of all energy input and output for land based cultivation
4.2.3 Energy inputs
4.2.3.1 General
With reference to Figure 5, the different energy inputs which can be used in land based algae cultivation
systems are described in this clause with the aim to identify relevant measurements and requirements
for evaluation of each energy flow and the overall balance across the green box.
4.2.3.2 Electric power
Electric power is the energy supplied to the green box through electricity. This power is always
quantified by a meter and can originate from an external source (transported by the grid) or a local
source. All electric power originates from a renewable source (wind turbines or solar panels) or a non-
renewable source (local CHP plants or external fossil powered electricity plants). Regularly electric
power is a mix of sources where the renewability of all individual sources shall be known in order to
perform any LCA calculation.
4.2.3.3 Solar energy
Solar energy is the energy directly put into the green box from solar radiation. Part of the photon influx
is converted into biomass and a part is transferred into heat. In practice solar energy cannot be
measured directly. Indirect measurements on biomass production (conversion ratio) and increase of
temperature through heat participation are ways to indicate the magnitude. With algal production solar
energy can also solely be used as thermal energy through culture heating. It cannot be measured
directly beside specific application of solar energy panels.
4.2.3.4 Chemical energy
Chemical energy includes all forms of energy inputs coming from free energy of reactants such as
organic substances fed to heterotrophic or mixotrophic systems and biofuels used as well as fossil
source fuels. It can be calculated from fiscal documents and conventional thermodynamics.
12
---------------------- Page: 14 ----------------------
oSIST prEN 17983:2023
prEN 17983:2023 (E)
4.2.4 Energy outputs
Algal heat value is the calorific value of dry matter as measured according EN ISO 18125. If the product
is wet or fresh algae, the amount of energy required to bring the water in the sample to vapor state in
reference conditions shall be deducted from the calorific value (i.e. balance performed on the basis of
the Lower Calorific Value).
Electric power is the energy fed to the grid usually sold and measured by fiscal meter(s), coming from
use of algal biomass or algae product(s) as source in power production system e.g. biogas or CHP
facility.
For uses as biofuels, the calorific value measurement shall be carried out according to EN ISO 18125.
Energy losses can be calculated by energy balance over the green box (see Figure 5).
4.2.5 Simplified energy balance, land-based cultivation
In phototrophic land based systems where only power and fuels provide energy for system operation
other than solar light, heat value can provide useful information of photosynthetic energy conversion.
The photosynthetic energy E stored in biomass is given by the Formula (1):
′
E= mH* / 3600 (1)
DW
where
E is the photosynthetic energy stored in biomass [kWh/yr];
m' is the mass flow of algae [kg/yr];
H is the heat value of dry matter sample [kJ/kg].
DW
When energy losses in output can be assumed or demonstrated to be negligible (10 % or 5 % of heat
value) it is possible to calculate the photosynthetic conversion efficiency η according the Formula (2):
η 100*E / PAR*A++W F (2)
( )
where
η is the photosynthetic conversion efficiency [%];
2
PAR is the yearly mean photosynthetic active radiation fraction of solar light [kWh/(m∗yr)];
2
A is the photosynthetic area [m ];
W is the electric power input [kWh/yr];
F is the fossil source power input.
Figure 6 illustrates a simplified energy balance of a land based cultivation.
13
=
...
Questions, Comments and Discussion
Ask us and Technical Secretary will try to provide an answer. You can facilitate discussion about the standard in here.