Parratt & Associates Scoping Biorefineries: Temperate Biomass Value Chains

3.3 Estimated costs and amounts of biomass from forests and crop residues produced

The analysis above suggests that three national assessment and two regional assessments use little original data and are reviews of existing data and reports, with some additional work done by consultants to fill in gaps for specific biomass types. This approach makes it difficult to assess the reliability and validity of the data and underlying assumptions.

The variability between the national and regional studies indicates the high degree of uncertainty associated with estimating total amounts of biomass produced from agriculture and forestry systems in particular. It also brings into question the proportion of the biomass that could be available as feedstock for biorefining.

Apart from the CSIRO Biofuels of Australia report¹⁰⁴, the sole focus of the assessments has been on stationary energy production. There has been no focus on the potential use of biomass feedstocks for bioproducts or a biobased industry. While many of the assumptions regarding feedstock amounts, types and costs are relevant to a range of potential downstream uses, specific characteristics of the feedstock that may be crucial in determining its potential suitability for a biorefinery (e.g. moisture content, density, lignin, cellulose and hemi-cellulose content) are ignored.

Key gaps in existing assessments therefore include;

• 
  a lack of accurate data on the total and available current production of many feedstock types (e.g. forest residues, wheat stubble, sawmill residues);
  
• 
  a lack of data on potential production from new biomass resources (e.g. mallee plantings, oilseed trees, algae), the potential location of these resources, and trade-offs with current land use systems;
  
• 
  a lack of data broken down to the state level or smaller on the production of different biomass types;
  
• 
  almost no data on the production, harvest or transport costs of different feedstock types, and
  
• 
  no information on key characteristics of different biomass resources that may influence their suitability as a feedstock for energy, fuel or other bioproducts.
  

There is limited information on which to base estimates of total biomass production for either agriculture or forestry. Further research could add some weight to previous reports but also to add clarifying assumptions on any estimations of biomass. Although ABARE publishes information on the total volume of wood sold for different forest types (i.e. softwood plantations, hardwood plantations and native forests) and products (sawlogs and pulp logs) at a national level, there is no disaggregated information available on the production of different log types at a state level¹⁰⁵. There is also no published information on the actual biomass (in dry tonnes) of logs harvested, the amount of harvest residues left on site, or production of residues from sawmills. This information must be derived from annual forestry agency reports, published estimates and expert opinion of recovery rates and residue production rates. Key assumptions used to estimate these factors are provided in Table 3-3. Unless otherwise stated, all figures for the amount of biomass feedstock are given in terms of oven-dry weight.

Data from ABARE was used to estimate the total amount of logs currently harvested from native forests and plantations at a state level as well as the average breakdown of sawlogs and pulp logs at a national level¹⁰⁶. This information was combined with figures from annual reports from state forestry agencies to disaggregate the different log types produced from native forests and plantations in each state.^107, Sawmill residue estimates were based on the amount of sawlogs harvested and published recovery rates for softwood and hardwood sawmills from a sawmill survey conducted by ABARE¹⁰⁸. Forest residues were estimated from the total amount of logs harvested and estimated residue factors (percentage of above ground biomass left on the ground as stems, branches and foliage) from forest managers^109, and published estimates for native forests¹¹⁰ and plantations¹¹¹.

A key assumption is the amount of material that could be theoretically harvested and removed without impacting future crop or forest growth or causing other negative environmental effects given no economic barriers. Here we assume that 70% of harvest forest residues (equivalent to the branch and foliage fraction) are left on site to supply organic matter and nutrients, or for soil protection with only the stem wood removed. We also assume that no sawlogs are available, although all sawmill residues and pulp logs are assumed to be available at a price.

Table 3-3: Key assumptions used to estimate biomass production from forests and crops

Parameter	Unit		Native forest		Plantations						Crop Residues
					Softwood		Hardwood		Mallee
Logs
^112^113Density	kg/m3		650		450	^25	550	^25	550		NDA
MC	% wet wt.		50	^31	55	^31	50	^31	45	26	NDA
Harvest residues
^114^115^116Proportion	% total above ground biomass		740		35		35	^28	NDA		64
^117MC	% wet wt.		50		55		50		NDA		15
Sawmill residues
^118^119Proportion		% sawlog	62		53	^31	62		NDA		NDA
MC		% wet wt.	45		45		45		NDA		NDA
Availability
Sawlog		%	0		0		0		NDA		NDA
Pulp log		%	100		100		100		NDA		NDA
Harvest residue		%	30		30		30		NDA		43	^129
Sawmill residue		%	100		100		100		NDA		NDA

MC = Moisture Content; NDA = not data applicable.

Stubble production from grain crops has been estimated by Dunlop et al.¹²⁰ Total production across Australia for the period 1983–2005 was estimated to average 51 Mt/y based on ABS figures for grain production and if a harvest index (ratio of grain to total above ground biomass) of 36% is assumed. The potential impact of removing harvest residues on soil carbon or future crop growth is not well understood. However, Dunlop et al. assumed that it would not be feasible to collect 15% of the stubble and a further 1–1.5 t/ha would be left on the ground to prevent wind and water erosion and to help maintain soil carbon and recycle nutrients. Thus, only 22 Mt/y or 43% of the total amount of stubble produced was estimated to be potentially available for harvest as a result of technological and environmental considerations. As there is no state-by-state breakdown of these figures, state-based grain production figures for 2008–09 from ABS¹²¹ were used to estimate stubble production. To obtain the state-by state breakdown an average harvest index of 36% and an availability of 43% is assumed when determining stubble production and that available for biomass transformation.

Estimates of future forest biomass production from existing plantations were based on figures from the National Plantation Inventory¹²². These figures are based on estimates from private and public plantation management agencies and are provided at a regional level for pulp logs and sawlogs from hardwood and softwood plantations. No state-by-state breakdown of future biomass production from potential future plantings is available. For dryland Mallee (E. polybractea and E. kochii), national estimates are from Bartle et al¹²³ based on dryland systems planted across a proportion (5%) of existing cleared land.

Table 3-4: Estimated current biomass production potentially available as biorefinery feedstock from southern Australia (kT/y oven-dry weight). Note: NSW includes ACT.

Forest and feedstock type		NSW	WA	SA	Vic.	Tas.	Total
Native Forest
	Pulp logs	400	140	-	510	1,870	2,920
	Forest Residues	270	80	-	300	610	1,260
	Sawmill Residues	410	110	-	410	350	1,280
	Total Native Forest	1,080	330	-	1,220	2,830	5,460
Hardwood Plantations
	Pulp logs	30	730	20	130	430	1,340
	Forest Residues	10	80	-	20	540	160
	Sawmill Residues	30	-	-	10	20	60
	Total Hardwood Plantations	70	810	20	160	500	1,560
Softwood Plantations
	Pulp logs	600	140	370	590	300	2,000
	Forest Residues	180	50	120	190	60	600
	Sawmill Residues	530	140	380	610	130	1,790
	Total Softwood Plantations	1,310	330	870	1,390	490	4,390
Crop residues
	Total Crop residues	2,800	3,700	1,300	1,000	-	8,800
Total Potential Available
	Pulp logs	1,030	1,010	390	1,230	2,600	6,260
	Forest Residues	460	210	120	510	720	2,020
	Sawmill Residues	970	250	380	1,030	500	3,130
Total Forest		2,460	1,470	890	2,770	3,820	11,410
Total Crops		2,800	3,700	1,300	1,000	0	8,800
Overall	Temperate Australia
		NSW	WA	SA	Vic.	Tas.	Total
Estimated Potential Biomass		5,260	5,170	2,190	3,770	3,820	20,210

With the provisos noted earlier (Table 3-1) the theoretical amount of biomass available from forests, plantations and sawmills as feedstock for a biorefinery could be up to 11.4 Mt/y (oven-dry weight, Table 3-4). This consists of 5.5 Mt/y from native forests, 1.5 Mt/y from hardwood plantations and 4.1 Mt/y from softwood plantations, and is made up of 55% pulp logs, 27% sawmill residues and 18% forest harvest residues (Table 3-3). The States with the largest amount of forest biomass are Tasmania (3.8 Mt/y) Victoria (2.8 Mt/y) and New South Wales (2.5 Mt/y) (See Figure 3.1). The estimated composition of residues from softwood mills is 58% woodchips, 13% bark, and 29% sawdust and shavings; while that for hardwood sawmills is 33% woodchips and 67% sawdust and shavings¹²⁴.

Figure 3-1: Percentage distribution of estimated current biomass production from Forest products potentially available as biorefinery feedstock from (% of Total estimated available) from southern Australia.

Based on the existing data for 2008-09 the amount of crop residue available as feedstock is estimated to be approximately 8.8 Mt/y. The amount was greatest in Western Australia (3.7 Mt/y) and New South Wales (2.8 Mt/y) with smaller amounts from South Australia (1.3 Mt/y) and Victoria (1.0 Mt/y) (See Figure 3.2). In other words, out of a total grain plus stubble production of 56Mt/yr of grain and stubble, 8.8Mt/yr is available for biomass transformation. These figures represent estimates based on one year’s crop production, and do not take into account the large year-to-year variability associated with variation in rainfall¹²⁵. They should therefore be treated with caution.

Figure 3-2: Percentage distribution of estimated current biomass production potentially from crops available as biorefinery feedstock from southern Australia.

Future wood harvests from existing hardwood plantations are expected to increase substantially as a result of new areas planted within the past 12 years reaching harvestable age. Data from the National Plantation Inventory¹²⁶ indicate that the total volume harvested from hardwood plantations is expected to increase to 14 million m/y (average 2010–2029), or by over 11 million m³³/y (6 Mt/y) compared with the current harvest. The amount of wood harvested from softwood plantations is not expected to increase substantially, and the amount of wood from native forests will likely also remain flat or decline.

For the period 2001–08 an average of around 26.5 million m³/y of wood was harvested and sold, mainly in the form of sawlogs and pulp logs nationally with 23.8 million m³/y from across temperate Australia (i.e. excluding Queensland and the Northern Territory). This latter amount consisted of 9.0 million m³/y from native forests 2.8 million m³/y from hardwood plantations and 12.0 million m³/y from softwood plantations¹²⁷. There is currently an inability to process most of the wood produced in Australia, despite a large deficit in the trade of wood and wood products (A$2B in 2006). Currently there are only two mills in Australia with the capacity to utilise plantation hardwood. Only 7% of Australia’s hardwood pulpwood is processed onshore¹²⁸.

Future biomass production from potential future plantings on cleared broadacre cropping land across southern Australia has been estimated to be up to 39 Mt/y¹²⁹. This estimate was based on a total planted area of 2.4 million ha (5% of the current area with crops or pasture) being planted with an estimated growth rate of 13–20 t/ha/y. These growth rates are much higher than estimated current growth (<1–8 t/ha/y) and are based on an assumed 20% increase in water use efficiency. Under the base case scenario with current growth rates, the total amount of biomass able to be produced from the same land area was 8 Mt/y. Of the total biomass production, 50% was from New South Wales, with 20% each from Victoria and Western Australia and 10% from South Australia.