我要种多少树才能解决全球变暖的问题?表明，仅仅靠种树来应对气候变化是多么不可思议(我们需要种植约6000万公里的树木——这是澳大利亚面积的6倍!)

但这是基于树木每年只吸收5.9公斤二氧化碳的假设，但在快速谷歌之后，似乎还有比这高许多倍的其他估计。

问题:CO$_2$吸收能达到多高-也就是说，哪种植物(或哪种植物的组合)吸收最多的CO$_2$每平方公里，这个数字大约是多少?

假设:

• 假设有利的环境，即植物最喜欢的条件
• 如果可能，假设<强>净植物一生的平均吸收率，以考虑到植物生长过程中不同的吸收率。以及植物在生长过程中释放一些碳

Humbertode Jesus Eufrade Junior等，“短轮矮林生长的桉树生物量的可持续利用”，生物量和生物能源， Vol. 90, July 2016, pp. 15-21

根据获得的结果，密度种植和施肥水平对干物质产量、能量产量和养分输出有更大的影响。高密度种植达到每公顷30.9吨干物质的平均值

Rafael Fiusa de Morais等，“直接生物质燃烧生产生物能源的象草基因型”，Pesq。agropec。胸罩。， Vol. 44, No.2, 2009年2月

这项工作的目的是评估大象草(Pennisetum purpureum Schum.)通过直接生物质燃烧生产生物能源的基因型。在两种不同的低肥力土壤类型中，对五种象草的基因型进行了评价。 [...] The dry matter yields ranged from 45 to 67 Mg ha^-1

There are 100 hectares in a square kilometer, and one Mg is one metric ton, so the reported annual yields correspond to 3090 tons per square kilometer for eucalyptus, and up to 6700 tons per square kilometer for elephant grass. Obviously the dry mass of plants is not just composed of carbon. The FAO provides this helpful data:

The carbon content of vegetation is surprisingly constant across a wide variety of tissue types and species. Schlesinger (1991) noted that C content of biomass is almost always found to be between 45 and 50% (by oven-dry mass).

Assuming 45% carbon content, this means eucalyptus trees can bind 1390 tons of carbon / km² / year and elephant grass can bind 3015 tons of carbon / km² / year. A CO₂ molecule has atomic weight 44 while carbon has atomic weight 12, so the CO₂ tonnage is the 3.66-fold of these numbers, that is ~5100 tons and ~11000 tons, respectively.