Biobränsle

Fossila bränslen måste ersättas av förnybar energi. Förnybar el kommer från energikällor som i snabb takt förnyar sig. Solens strålar kan nyttjas direkt till solkraft. Eller indirekt till vindkraft och vattenkraft. Den enda förnybara energikälla som inte är beroende av solen är tidvattenkraften, där det främst är månens gravitation som skapar energin.

Fossila bränslen, det vill säga, kol, olja och gas, har skapats under en så lång process att vi inte kan ersätta den mängd vi förbrukar. Biobränslen däremot är förnybara. 

På världsnaturfonden förklaras biobränslen såhär: ”Biobränslen är ett samlingsbegrepp för bränslen som har det gemensamt att de tillverkas av organiskt material, det vill säga växter, slam från reningsverk eller slaktavfall. Biobränslen fungerar som energibärare ur vilka man kan utvinna energi. Biobränslen kan vara gasformiga som biogas, flytande som etanol eller fasta som exempelvis ved och pellets. Att tillverka biobränslen av avfall eller av restprodukter inom jordbruket är ofta mest optimalt för miljön och klimatet. När biobränslen tillverkas av skogsprodukter är risken däremot stor att produktionen inte sker hållbart, som när regnskog skövlas och ersätts med oljepalmsplantager.”

Hampan som biobränsle, är i en doktorsavhandling satt under lupp:

“Originally approved for fibre production, industrial hemp can also be used for production of renewable energy carriers, such as solid biofuel, biogas and bioethanol. With its potentially high biomass yield and its suitability to fit into existing crop rotations, hemp could complement and exceed other available energy crops. Because of the reignited interest in hemp there is now a need for re-establishing knowledge about its cultivation and harvest, but also about its new applications as an energy crop.” Industrial Hemp (Cannabis sativa L.) –a High-Yielding Energy Crop SLU publication database (SLUpub) av Thomas Prade.

Här är avhandligens abstract: (citerat med tillåtelse av författaren)

Abstract

Bioenergy is currently the fastest growing source of renewable energy. Tighter sustainability criteria for the production of vehicle biofuels and an increasing interest in combined heat and power (CHP) production from biomass have led to a demand for high-yielding energy crops with good conversion efficiencies. Industrial hemp was studied as an energy crop for production of biogas and solid biofuel. Based on field trials, the development of biomass and energy yield, the specific methane yield and elemental composition of the biomass were studied over the growing and senescence period of the crop, i.e. from autumn to the following spring.

The energy yield of hemp for both solid biofuel and biogas production proved similar or superior to that of most energy crops common in northern Europe. The high energy yield of biogas from hemp is based on a high biomass yield per hectare and good specific methane yield with large potential for increases by pretreatment of the biomass. The methane energy yield per hectare is highest in autumn when hemp biomass yield is highest.

The energy yield per hectare of hemp for use as a solid biofuel is highest in autumn when the biomass yield is highest. However, important combustion-related fuel properties, such as moisture, alkali, chlorine and ash content and ash melting temperature, are significantly improved when industrial hemp is harvested in spring instead of in autumn. Major fuel properties of hemp are not significantly influenced by annual cultivation conditions, latitude or choice of cultivar. Net energy yields per hectare and energy output-to-input ratios of hemp are above- average in most applications, and are highest for use of hemp as solid biofuel. Use of hemp as a biogas substrate suffers from higher energy inputs and lower conversion efficiencies, but produces a high-quality vehicle fuel.

Advantages over other energy crops are also found outside the energy balance, e.g. low pesticide requirements, good weed competition and suitability as break crop in cereal-oriented crop rotations. Improvements in hemp biomass and energy yields may strengthen its competitive position against maize and sugar beet for biogas production and against perennial energy crops for solid biofuel production.

Keywords: bioenergy, fibre hemp, feedstock, solid biofuel, biogas, substrate, biomass yield, energy yield, energy balance, production

Läs också

Hemp as a potential raw material toward a sustainable world: A review: Heliyon

Environmental Benefits | EIHA

EIHA | Only pan-European membership organization in the industrial hemp sector

Hemp – European Commission

Hampans miljöegenskaper Hampa i kläder och textil Hampa som byggmaterial Hampa som energikälla Hampa som livsmedel Hampa vid djurhållning Att odla hampa