VOA慢速英语2009年-Agriculture Report - Making Better Con

This is the VOA Special English Agriculture Report.

Rice hulls², or husks, are the protective coverings on grains of rice. Rice with just its hull¹ removed is brown rice. Rice without its hull or bran is white rice.

Once rice is harvested, the hulls are out of a job. They may be taken to landfills or burned. Sometimes they are used to absorb waste in chicken houses. Other times they are used to amend³ soil.

But a chemist in Texas has another idea.

Rajan Vempati led a group that developed a new process to make rice hulls into ash. The idea is to replace some of the portland cement traditionally used in making concrete. Portland cement is a material that holds together the sand and crushed stone in concrete.

Rajan Vempati thinks rice hull ash could help the concrete industry produce less carbon dioxide. Carbon dioxide is released in cement manufacturing when fuel is burned and limestone⁴ is heated. The Portland Cement Association says the gas from the limestone is reabsorbed as concrete ages.

But cement manufacturing produces around five percent of the carbon dioxide released by human activity worldwide. Carbon dioxide is one of the gases that may affect the climate by trapping heat.

The process for making rice hull ash heats the hulls to eight hundred degrees centigrade. Carbon is driven out, and fine particles of almost pure silica remain. The process releases some carbon dioxide, but Rajan Vempati says it would be reabsorbed into the soil naturally.

Another inventor, Prasad Rangaraju, is an engineer at Clemson University in South Carolina. He tested the cement, and says less could be used because the rice hull ash makes it a stronger building material. Also, the inventors say the light-colored material better reflects sunlight, so buildings would cost less to cool.

The National Ready Mixed Concrete Association points out that using ash in cement is not a new idea. The ancient Romans discovered that volcanic⁵ ash made better cement.

But the modern inventors say rice hull ash works better than other materials. They developed the process with money from the National Science Foundation. They have not yet brought it to market.

Rice hull ash is already available, but the product is relatively⁶ costly⁷.

Cost, including transportation, may decide the success of the new technology. Using it could make the most sense in areas where farmers grow lots of rice and the hulls might just go to waste.

And that's the VOA Special English Agriculture Report, written by Jerilyn Watson with Steve Baragona. I'm Bob Doughty⁸.
 

1 hull   

n.船身；(果、实等的)外壳；vt.去(谷物等)壳

参考例句：

• The outer surface of ship's hull is very hard.船体的外表面非常坚硬。
• The boat's hull has been staved in by the tremendous seas.小船壳让巨浪打穿了。

2 hulls   

船体( hull的名词复数 )； 船身； 外壳； 豆荚

参考例句：

• Hulls may be removed by aspiration on screens. 脱下的种皮，可由筛子上的气吸装置吸除。
• When their object is attained they fall off like empty hulls from the kernel. 当他们的目的达到以后，他们便凋谢零落，就象脱却果实的空壳一样。

3 amend   

vt.修改，修订，改进；n.[pl.]赔罪，赔偿

参考例句：

• The teacher advised him to amend his way of living.老师劝他改变生活方式。
• You must amend your pronunciation.你必须改正你的发音。

4 limestone   

n.石灰石

参考例句：

• Limestone is often used in building construction.石灰岩常用于建筑。
• Cement is made from limestone.水泥是由石灰石制成的。

5 volcanic   

adj.火山的；象火山的；由火山引起的

参考例句：

• There have been several volcanic eruptions this year.今年火山爆发了好几次。
• Volcanic activity has created thermal springs and boiling mud pools.火山活动产生了温泉和沸腾的泥浆池。

6 relatively   

adv.比较...地，相对地

参考例句：

• The rabbit is a relatively recent introduction in Australia.兔子是相对较新引入澳大利亚的物种。
• The operation was relatively painless.手术相对来说不痛。

7 costly   

adj.昂贵的，价值高的，豪华的

参考例句：

• It must be very costly to keep up a house like this.维修这么一幢房子一定很昂贵。
• This dictionary is very useful,only it is a bit costly.这本词典很有用，左不过贵了些。

8 doughty   

adj.勇猛的，坚强的

参考例句：

• Most of successful men have the characteristics of contumacy and doughty.绝大多数成功人士都有共同的特质：脾气倔强，性格刚强。
• The doughty old man battled his illness with fierce determination.坚强的老人用巨大毅力与疾病作斗争。