Consistent with EISA, USDA assumes that biomass may be grown on defined agriculture cropland (agriculture cropland where crops are produced and agriculture cropland in pasture). To produce this much in biofuels will take 27 million acres of cropland,3 6.5 percent of the total

406.4 million acres of cropland as reported in the 2007 Census of Agriculture (COA). This does not include acreage of timberland harvested from which logging residues are viable feedstocks,

nor does it include acreage from traditional food crops from which post harvest crop residues are collected.  Importantly, USDA will assess the acreage of fallow and underutilized lands that can be sustainably converted into dedicated energy crops.

 

Cropland. The UDSA’s 2007 COA reports that there is a total of 922.1 million acres of Land in Farms.  The category land in farms is comprehensive and represents all land in farms: land that is defined as agriculture cropland (406.4 million acres) and other land (515.7 million acres). Cropland is further segmented into the following categories:  cropland harvested, cropland used as pasture (land that could be planted, but is in pasture the year of the COA), other crop land that is idled for conservation or intentional purposes, summer fallow, and failed crops. Cropland harvested is the larger category accounting for 76 percent of the total cropland.

 

 

 

 

EISA provides a definition of renewable biomass that is more restrictive than the Farm Bill definition of renewable biomass.  EISA restricts where feedstocks can grow and be harvested for use in producing renewable fuels for compliance with the RFS2.  For planted crops/crop residue from agricultural land and planted trees/tree residue from actively managed tree plantations on non-federal land, feedstocks must come from land cleared/cultivated land prior to December 19,

2007.  EPA’s approach excludes rangeland as an approved land type from which renewable

biomass could be produced or harvested.

 

Forested land. USDA estimates of biomass from logging residues are based on actual data from the 2001 – 2005 period.  The average annual volume of logging residues (all species), average over the 2001-2005 period, is assumed available per annum.  The total and harvested timberland area is also averaged over 2000-2005 period to give an estimate of the area that logging residues actually come from and, potentially, how large or how much biomass might be available.  For

the purposes of this analysis 42.5 million dry tons of logging residues, used for no other purpose and totaling only a percentage of the total logging residues actually generated by logging practices, is available for fuel production annually.  This residue is taken from 10.8 million acres of harvested acreage, as compared to the 507.3 million acres of timberland available for harvesting activities.  One dry ton of logging residues is assumed to yield 70 gallons of ethanol per dry ton.  In total, about 2.8 billion gallons of advanced biofuels is projected from logging residues when the conversion technology is commercialized.

 

The document about Land Use Assumptions and Limitations was translated by Huayiwang Mandarin Translation Company.

 

 

与《能源独立与安全法》一致，美国农业部假设生物质可以是在规定的农业耕地（也就是生产农作物的农用耕地，以及牧场中的农业耕地）上生长起来的。要生产出目标所规定数量的生物燃料，需要占用2,700万英亩的耕地³，这在2007年农业普查（Census of Agriculture，COA）所报告的4.064亿英亩耕地总面积中占6.5％，其中并未包括能够从其中的伐木残留物中获取可用原料的已采伐林场面积，也未包括能够从中采集收获后作物残余物的传统粮食作物耕地面积。美国农业部还将对那些能够持续生产专用能源作物的休耕地与利用不足的土地面积做出评估，这是相当重要的一项工作。

 

耕地。美国农业部2007年的农业普查报道，农业土地（Land in Farms）的总面积是9.221亿英亩。“农业土地”这种分类是比较全面的，它涵盖了所有的农业土地，既包括被定义为农业耕地的那些土地（4.064亿英亩），也包括其它土地（5.157亿英亩）。

耕地又被进一步细分为以下几类：收获耕地、用作牧场的耕地（可以种植作物、但在农业普查的这一年却用作牧场的土地）、为保护起见或有意闲置的其它耕地、夏季休耕地以及欠收耕地（failed crops）。收获耕地是其中最大的一类，在耕地总面积中占了76％。

 

 

农业耕地（单位：千英亩）

对于可再生生物质，《能源独立与安全法》做出的定义比《农场法案》（Farm Bill）所做的定义局限性更强。《能源独立与安全法》限定了为满足可再生燃料标准第二阶段的要求而用来生产可再生燃料的原料能够在哪些地方生长并收获。对于来自农用土地的种植作物、作物残余物，以及来自不属于联邦政府土地上有效管理的林木庄园的种植树木、树木残留物，如果作为可再生燃料原料，那么就必须来自2007年12月19日之前开垦、耕作的土地。美国环境保护署在可以生产或收获可再生生物质原料的认可土地类型中排除了牧地。

 

林地。美国农业部对来自伐木残留物的生物质做出的估计，依据的是2001－2005年间的实际数据。在这一期间的年均伐木残留物体积（所有树种）假定是每年都可以使用的。为了估计实际产生伐木残留物的林场面积，并估计这些林场有可能提供多大体积的、或是多少生物质，林场的总面积及采伐林场的面积也在2000－2005年间取平均数。从这份分析报告的角度出发，我们假定每年燃料生产可用的伐木残留物（不投入任何其它用途）为4,250万干量吨，它们在伐木作业中实际产生的伐木残留物总量中只占一个百分点。这些残留物取自1,080万英亩的已采伐林地，而相比之下，可用于采伐的林地面积是5.073亿英亩。每干量吨的伐木残留物假设可以生产70加仑的乙醇。那么，在这种能源转化技术实现商业化后，从伐木残留物中生产的先进生物燃料总数估计就会达到28亿加仑。

 

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