During the 19th century, the demand for ivory billiard balls decimated elephant populations, forcing chemists to look for a synthetic alternative.

19 世纪时期，象牙制的台球让大象数量锐减，迫使化学家寻找合成替代品。

This week, a non-profit that set standards for American-made medicines proposed new rules for using the synthetic alternative.

本周， 一家为美国制造的药品制定标准的非营利组织提出了使用合成替代品的新规则。

Synthetic alternatives, made from carbon captured from industrial sources or directly from the air, are so far the preserve of a few pilot projects.

合成替代品， 由从工业来源或直接从空气中捕获的碳制成，迄今为止是少数试点项目的专利。

But research published in April found that when compost is used as a fertilizer, it fights off disease-causing bacteria better than synthetic alternatives—even if it's made with manure or animal bones.

但 4 月份发表的研究发现， 当堆肥被用作肥料时，它比合成替代品更能抵抗致病细菌——即使它是用粪便或动物骨头制成的。