Why does PoW matter in the first place. We know that it is tried and true method for cryptocurrency security. We know that it works really well. But why did it become a thing in the first place? So it's a quick tech-history lesson:

Decentralized Ledger Technology requires someone to edit the ledger periodically. So who gets to edit? You can't make it random because it's easy to Sybil attack. One person could setup hundreds of nodes and get the chance to edit more and more times. A government or a large corporation would easily be able o take over the network. Hence it is not secure. If we could build a mathematical problem that is hard to solve but easy to verify the accuracy of, we can ask the world to simply brute force the solution. This way, the person/entity who commit the most amount of resources gets most of the chances to edit the ledger and claim Tx fees and newly created coins.

But It is All Intrinsically Meaningless

Yes you get your security for the network. You also drive innovation. GPUs have greatly evolved in the recent years and cryptocurrency mining is one significant element that kept driving this innovation. But at the end of the day it is a stupid math problem. It's like congress gathering where they decide the speaking order by playing a massive championship league of Rock-paper-scissors or Tic-tac-toe. You do finally use the results of these matches for a very valuable thing. But the games themselves are in no way related to the congress activities.

Why Can't PoW Solve Real Problems With Computing Power

The difficulty of mathematics problems can be adjusted in order to create a predictable block time. You can't adjust the difficulty of real world problems. You might also run out of real world problems temporarily.A research could simply wrap up and humanity could face a massive gain. But there would be less stuff to work on.

Byteball DAG + World Community Grid

World Community Grid (WCG) is an effort to create the world's largest public computing grid to tackle scientific research projects that benefit humanity. Launched on November 16, 2004, it is co-ordinated by IBM with client software currently available for Windows, Linux, macOS, and Android operating systems. Using the idle time of computers around the world, World Community Grid's research projects have analyzed aspects of the human genome, HIV, dengue, muscular dystrophy, cancer, influenza, Ebola, virtual screening, rice crop yields, and clean energy. As of March 2018, the organization has partnered with 449 other companies and organizations to assist in its work, has over 52,000 active registered users, and a combined total run time of over 1.5 million years.

• Wikipedia

I described the process in my post titled Why I Stopped Mining and Started Earning Byteball and it's easy as setting up a one click miner.

The Advantages

• CPU mining has been made obsolete by GPUs and ASICs. But ASICs are optimized to do nly one thing really well. So WCG does require user's CPUs and GPUs.
• You can put your old devices to work while you are minding your own business. Your workflow won't really be affected by running WCG Client in the background.
• Your rewards are calculated in USD; not Bytes.

The last bullet point is very important. Byteball is the best DAG I know of. They have already working human readable smart contracts, chat bots and a whole eco-system. All Bytes were Pre-mined and the WCG contributions are used as a way to distribute the funds to more people. The price has dropped by almost 95% from peak and a massively valuated project like IOTA can't even begin to imagine competing with a project like Byteball.

The Blessing of The Bear Market

You are not suppose to make a profit contributing to WCG. You are not going to make a profit mining on you laptop or mobile devices either. You will also have to wait till you accumulate some crypto to transfer them to your wallet. Byteball sends your rewards almost daily and directly to your wallet. You get about $1 worth Bytes per 100,000 WCG Points. Longer the bear market last, the more Bytes you can accumulate.

Proof of Charity Work

You can't build a blockchain based on this. There are so many complications which I won't describe here. But a powerful existing system can be leveraged to help to make the world a better place. I didn't even know about World Community Grid before I got into Byteball. The infrastructure is cheap to maintain but the network is highly valuable. When you think about STEEM, 75% of the newly minted STEEM goes to content producers and voters. Byteball + WCG takes this to a different level where you are incentivized to contribute to real scientific research with the idle resources of your computing devices. That's a smart ecological move where the burned energy produce something of value instead of wasting it like PoW.