Andries van der Linde Director Millennium Energy South Africa

Transcription

1 Andries van der Linde Director Millennium Energy South Africa

2 WOOD AS FUEL SOURCE FOR POWER GENERATION

3 BIOMASS AS A FUEL SOURCE Wood a fuel source since fire was discovered? Still only source for some rural communities Biomass to electricity not new especially bagasse use Mauritius e.g. 480MW from bagasse (Seasonal) Sweden - 1,500MW from wood (4.5%) Austria 750MW

4 BAGASSE USE IN SOUTH AFRICA Sugar refineries the ideal industry for cogeneration In-house requirements 700GWh Potential 3,000GWh from bagasse Total potential on sugar biomass 5,500GWh if tops and trash is included Disadvantage seasonal and has to be coal subsidised

5 ESKOM CARBON FOOTPRINT Eskom mainly dependent on coal 234,477GWh produced 94% Coal CO2 emissions approx. 230Mt N2O emissions approx. 2906t SOx emissions approx. 1810kt NOx emissions approx. 977kt

6 INHERITED CARBON FOOTPRINT Energy intensive industries particularly affected Transnet Electric locomotives Chemical Industries Mining Iron and steel Aluminum (Down side Eskom emissions used as base line)

7 COAL USE AND RESOURCES Eskom objective to peg coal use at 141mt by 2018 Concerns about coal availability Last coal resource assessment done in 1970 Council for Geoscience and mines currently compiling coal resource data base More efficient power stations Alternative technologies Biomass not mentioned

8 HISTORICAL COAL USE

9 WOOD OR COAL Coal started out as organic matter including wood Silica or other mineral absorption determine coal mineral content A direct comparison between coal and wood is possible e.g. Composition Calorific value

10 COMPARITIVE VALUES Ash content wood 0.6% Ash content coal 29% (Ash - Un-burned minerals) Calorific value wood 19 to 22MJ/kg Calorific value coal 19MJ/kg Sulfur content wood 18 times less than coal CO2 Wood is carbon neutral

11 HOWEVER Moisture content plays a significant role i.r.t. calorific values E.g. Eskom claims re rain in 2008 a real challenge Moisture dilutes energy content of fuel Uses/wastes energy when evaporated to join stack emissions

12 COMBUSTION PROCESS When wood burns a number of changes takes place: Wood dries absorbing energy As temperature increases some compounds volatilize These burn to yield CO2 and to produce energy leaving a small amount of ash

13 MOISTURE ENERGY LOSS Reduction in energy can be significant Latent heat of evaporation 2.442MJ per ton Resultant heat energy loss can be as much as 20% Ideally wood or wood waste should be dried However, this can also consume vast amounts of energy (Bagasse used as is with moisture content up 50%. Of 20% condensation loss, 14% from this.)

14 TREE SPECIES Soft woods: Burns readily because of its lower density Resin can add 10% to 20% to calorific value Hard woods: Higher energy density Oils and gums can have the same effect as resins in softwoods Bark: High ash content As much as 10%

15 VOLUME VERSUS MASS Density varies from species to species However, calorific value per unit weight is same but slightly higher for softwoods I.e. with soft woods a larger volume of wood is required to produce the same heat energy Approximately 2 times When wood waste, such as saw dust, wood chips etc. is included, additional challenges comes to mind

16 LOGISTICAL USSUES Important business case consideration Transporting wood is also energy transportation I.e. the less dense wood is the higher the volume and the less energy per load The business case for transporting wood waste is even worse because of is low density I.e. waste will have to be compacted In addition the transportation of wet wood will reduce the energy density further

17 JOB CREATION Considering logistics the job creation potential is massive Alien invaders such as black wattle covers more than 10 Million hectares This 8% of the country This is expected to double over the next 15 years At present approximately 20,000 people employed to try and eradicate these However, most of the wood is just left to rot

18 WOOD WASTE Forrest waste 3.13 Million tonnes Saw mill waste 2.9 Million tonnes Vast amounts of accumulated waste GHG impact Methane avoidance Carbon neutral Disadvantages: Distributed Poor mass to volume ratio

19 CONCLUSION Industrial data readily available - last study 2004 Eskom initiated a study in 2010 Alien invader data mostly based on estimates Accumulated waste quantities unknown and at best can only be estimated I.e. it is difficult for real and accurate conclusions on the impact of electricity from wood This would apply to the business case Wood as a percentage of coal relatively unknown